In Sumatra: Notes From a Geologist in the Field

By Kerry Sieh, Robert P. Sharp Professor of Geology

From January 3 to January 20, 2005, I was in Indonesia, focusing on Sumatra and its accompanying islands, to assess the geological changes caused by the Aceh earthquake and determine future locations for seismic monitoring equipment. Sumatra is one of the focus areas of the Caltech Tectonics Observatory, and this postseismic survey was funded by a grant from NSF.

This part of the world is familiar terrain to me; I studied the active Sumatran subduction zone for more than a decade. Last summer, my colleagues and I distributed brochures to people living on local islands to explain the area’s geology, and suggest ways to limit future damage. Now, in these occasional e-mail messages sent to Caltech during that time, I share my personal observations and preliminary science findings.

Among the debris at Sirombu, Nias, two men are building a temporary structure to house them while they build more permanent replacement for their lost home.

Monday Morning, January 3, Jakarta

Me at the helicopter, Lasikin airport, southern southwestern coast of Simeuleu island.

I arrived in Jakarta late in the morning yesterday, nearly a day after departing Los Angeles. Just walking around this bustling capital city of Indonesia, one would not know that a major disaster had struck the northwestern corner of the country just a week ago. In the evening I met with Danny Natawidjaja and Bambang Suwargadi, my colleagues from the Indonesian Institute of Science (LIPI), to compare notes on our preparations for fieldwork in western and northern Sumatra.

We knew several days ago from friends in Padang, the large coastal city of West Sumatra, that it had escaped damage from the tsunami. Now there is additional good news from two sites on the Mentawai and Batu islands, where we have GPS stations and many local friends. Our friends in Sikakap, the main town of South and North Pagai islands, report that the tsunami was only about a meter high and did not injure anyone, but did flood stores and homes. A similar story comes from Tello, the main town of the Batu islands: Relatives of friends of Danny report that the tsunami washed into the main street but caused no injuries. Both of these towns are on the east coast of their islands. We still have no word from friends in the villages on the more exposed western coasts of the islands, but fear that the tsunami height will have been greater there.

In Padang, there are reports that many people fear that a large tsunami will soon devastate the city. Large tsunamis did strike the city following the giant earthquakes of 1797 and 1833, so their fears are not baseless. But we have no basis for believing that such an event is imminent. We expect to have discussions with local officials about these concerns when we arrive on about January 6th. Even if there is no imminent threat to Padang, we know that it will be in a precarious position when the Mentawai section of the megathrust, just offshore, next ruptures. I wonder what urban planners and civic authorities should do in a situation like this?

We are hoping that a subset of our group will begin to download the SuGAr stations on the 6th, starting with Jambi in eastern Sumatra, then going on to the three stations on the mainland south of Padang. Simultaneously, another subset of the group would conduct a reconnaissance by fixed-wing aircraft of Simeuleu and neighboring small islands, expecting to see evidence of uplift, if these islands were above the rupture. We also hope to reconnoiter the west coast of Aceh, to survey evidence for submergence east of the megathrust rupture. We would like to get a few measurements of vertical deformation in both areas, to help guide a mission to document more thoroughly the deformation pattern. But we are not sure if the dire humanitarian situation on the coast of Aceh will allow us to make measurements on the ground. CNN reported yesterday that Simeuleu has survived the quake and tsunami relatively well, and that islanders there have a tradition of running for high ground when they feel a big earthquake, based upon their ancestors’ experience in the 19th century. On about the 9th, we hope to begin downloading SuGAr stations on the Mentawai and Batu islands by helicopter.

Today, we hope to meet with representatives of Bakosurtanal to coordinate plans to resurvey geodetic monuments in the source region. We also expect to meet with aviation companies to discuss arrangements for our fixed-wing and helicopter flights.

Seaward part of Muarasaibi and old coconut rootballs in water at Saibi.

Tuesday Evening, January 4, Jakarta

Water mark on wall of a home in a village. This mark was the level of stable water for several hours. The highest water was a few tens of cm higher. Zamzami is the 55-year-old local man on the right.

So far, everything is coming up roses with respect to getting our official travel permits from the scientific organization (LIPI), the political offices (Sospol), and the national police (PolRI).

Yesterday we had a press conference at the headquarters of the company that is partnering with us to develop telemetry (Pasifik Satelit Nusantara). About 60 print and television journalists attended to listen to Danny and me explain the science of the megathrust that produced the December 26th earthquake. Many stations broadcast the conference. One station caused a panic in Padang by editing Danny’s comments in such as way as to make it sound as if we thought a giant tsunami was imminent there. Danny was scheduled to go on national TV tonight, live and un-editable, to attempt to quell concerns. We are going to be in Padang and on the nearby islands in less than a week, so obviously we think the likelihood of another giant earthquake and tsunami is very small.

Yesterday we also met with a prominent former minister and a former ambassador to discuss the trouble in Padang and to discuss the longer-term problem of how to mitigate the effects of the eventual earthquake and tsunami there. We also met with the head of LIPI to discuss our desire to reconnoiter the stricken area by helicopter rather than by boat and on foot. Today, the heads of the office, Pak Jan and Pak Umar, told us that they have arranged with the military to move us around in a helicopter for the time that we are in Aceh. We need to firm this up and discuss the particulars tomorrow.

For our downloading of SuGAr stations south of the equator, we contracted today with a private helicopter company to take to the island stations between January 9 and 12. It will be strange to see from a fast helicopter the islands that we have visited so many times by slow boat. Today, while calculating our itinerary, I could not get used to the fact that distances that usually take us a 12 hours to traverse by sea will take us only an hour or so by land.

We learned that two teams of surveyors from Bakosurtanal, the national surveying agency, were to have flown to Nias today to begin their resurvey of the GPS geodetic monuments that Yehuda Bock and Indonesian colleagues used in their GPS research. They will recover spectacular evidence of coseismic deformation from the region of the earthquake, I am sure.

We have pretty much decided to install the four new continuous GPS stations on Nias, Simeuleu, and on the mainland Aceh coast, to monitor post-seismic transients. Originally, these new stations were to go in south of the equator, to densify the existing network.

The meeting today with the vice president of Indonesia lasted over an hour. We explained the potential scientific value of the continuous GPS network for monitoring the “heartbeat” of the Sumatran megathrust and suggested an international meeting within a month or two to bring together scientists from around the world who were working on various aspects of the earthquake and its effects. The vice president asked about the value of an early detection and warning system for tsunamis. We suggested that it would be in the best interests of the Indonesian people to make sure that such a system for the Bay of Bengal be able to issue a warning within a minute or so, since the tsunami could arrive on the shores of western Sumatra and its islands within just minutes of the occurrence of an earthquake.

What a joy it was yesterday evening to treat myself to a short jog on the treadmill and a little bit of exercise after a day spent driving around Jakarta in taxi cabs and being in meetings! No such luck tonight–the meetings weren’t over until after 10 pm.

It appears that we will arrive in Padang on January 7th and fly out to the islands on the 8th.

Zamzami, a local man, says that since the tsunami the beach has moved landward. Danny (on left of group) is standing where edge of grass was prior to the earthquake. Zamzami asserts that this erosion has taken place since the tsunami, not during.

Thursday Morning, January 6, Jakarta

Yesterday afternoon, the hotel was flooded with delegates to the international conference on relief for the earthquake and tsunami victims. All are walking around with big placards on their chests, color-coded to indicate the country they represent. Earlier in the week I was nearly alone on the 5th floor of this hotel. Now I share it with the Myanmar delegation and two Indonesian security officers, who are in the hallway all day and night, protecting the delegates. They look pretty bored, so I talk to them in my very broken Indonesian as I’m coming and going, to make their day a little more interesting.

Logistics are in their final stages. Rifki, from PSN, just brought us two more satellite phones, so the various subgroups of the team can keep in contact with each other during the helicopter downloads on the islands. Galetzka is stuck in Singapore, trying to get his visa in less than the typical two-day turnaround. The chairman of LIPI sent a special letter to the Embassy yesterday afternoon, pleading that the visa granting be expedited, since John’s participation in our work in the stricken region is essential to our success. Looks like it’s not going to happen, anyway. I just met with Cecep, the Indonesian geodesist from Bakosurtanal (the national surveying agency) and Yehuda’s principal collaborator, to coordinate our GPS work. We’ll do the continuous measurements; he’ll focus on reoccupation of the old monuments that Bako and Yehuda Bock’s group surveyed back in the 1990s. They will see huge changes across northern Sumatra, I’m sure; we’ll see small changes, since the SuGAr network is more than 300 km south of the rupture area.

Yesterday a few geologists forwarded me an article by a reporter who had interviewed me before I left Caltech. I was amazed to learn that someone could do such a thorough job of misrepresenting what I had said, even to the point of inventing quotations. I guess the hunger to dramatize and sensationalize is as strong as the desire to eat.

When I woke this morning, I found in my e-mail inbox a message from one of my friends in Padang, a city of nearly a million people on the western coast of Sumatra. It is in a setting not unlike that of Meulaboh, the western Aceh city that was devastated by the tsunami. It is directly landward of the giant earthquakes that we have been studying with corals and GPS, and has a history of giant tsunamis. The most recent big ones were in 1833 and 1797.

Madi, my friend, is a young guy who works in the hotel where our group often stays. He earns about a dollar a day making up rooms and doing other tasks there. Here is his e-mail to me:

“kerry apa kabar,you know i’am afraid if the happent come here, i’m not care about myself, but my parents and sister, you know the tsunamis issue will come here many people say like that now, so my father got accident last week, his left feet was broken, it’s very hard to me, I hope you can give me about the information, what will happent here after that, I know you are very busy with this situation, so I saw you in metrotv yesterday with mr.Denny, thanks kerry, see you, madi”

For the past four days, there has been much panic among the residents of the city, because they fear that a tsunami may be imminent. We are hearing reports that some people, like Madi’s father, have actually been injured. One reason for the panic is that people don’t realize that any such tsunami would be presaged by a very large earthquake.

Our posters and brochures and our lectures in churches and schools have thus far been restricted to the islands offshore of Padang, where the towns are small and it is easier to educate. We had been in discussions with the authorities in Padang last July and August about how best to educate this much larger population. The situation is particularly difficult because there is no way that, even with a 15-minute warning from the earthquake itself, most of the city’s inhabitants could escape landward.

On the scientific front, I was excited to get from Joann Stock a report that Roger Bilham filed, stating that in the Andaman islands, the west coast appears to have risen and the east coast submerged during the earthquake. This would mean that the rupture did, indeed, propagate as far north as the Andamans. This must be considered good news for the residents along the coasts of the Bay of Bengal, because it means that most of the subduction zone between Myanmar and northern Sumatra ruptured during the earthquake. Thus, the likelihood of another giant tsunami is probably not very high. Chen Ji also forwarded a report stating that an island in the Nicobar chain rose 3 meters, exposing the coral. Both of these reports describe landward tilting of the outer-arc islands, just like we see in the ancient corals off West and North Sumatra during large earthquakes there in 1797, 1833 and 1935.

I was delighted and relieved to have an e-mail from our Mentawai friend, Juniator Tulius, yesterday evening, saying that he and his wife had just arrived in Padang from the islands, safe and sound. He reports that a small tsunami occurred at Saibi after the earthquake, but that it didn’t even flood the houses. He also said that he and the villagers didn’t even feel the earthquake. He also reports no damage or loss of life at Tuapejit or Sioban, on the east side of Sipora island. But he has heard no word from villages on the west coast of the islands. Galetzka said today that he felt the earthquake way to the north, near the Burmese/Thai border. And an American friend of mine, who runs a hotel on the harbor in Padang, said over the phone to a reporter that she saw the tide flow out rapidly after the earthquake. I’m sure we’ll have many more stories to tell once we get to the islands.

Water flooding grass on sandy back beach just south of entrance to Salur village. Locals sitting nearby say there never was water here before the earthquake. Indicates submergence of at least 30 cm, we think.

Salur village from the air. Southwestern coast of Simeuleu.

Friday Night, January 7, Padang Hotel, Padang

So finally I have left Jakarta for the west coast of Sumatra. The rest of the crew follows on Saturday morning. First good news of the day was that Galetzka got his visa in Singapore and will be arriving in Jakarta in the early afternoon. Bambang, our main logistics guy, was nervous about being able to get the two requisite permits from government offices late on a Friday afternoon.

Stepping off our superannuated 737 at the airport in Padang, I saw a familiar scene—a dozen porters in green overalls ready to pounce as we entered the terminal and began the raucous process of claiming our baggage. After I found my bag, I waded through the crowd and found our longtime logistics assistant, Imam, and his wife, Susi, waiting for me. We loaded my bag into the “Imam-mobile,” his old clunker that miraculously still functions, and we were on our way to the little white Padang Hotel. We are staying in the one-story part of the hotel, about a kilometer from the beach. Our old favorite, the Tiga-Tiga Hotel, burned about a year ago. It was only about 500 meters from the beach, across the street from the main bus terminal. The bus terminal was moved to a more remote location on the edge of the city about two years ago, and now I see that an enormous new market place (pasar) is being built in its place. It is four stories tall and made of the standard materials—concrete pillars and beams, with an abundance of fill-in brick. I see a shear wall running perpendicular to the beach, but I have no idea how it will fare in a giant earthquake.

Our first snag this afternoon was when we attempted to change U.S. dollars to Rupiah, for buying the dry food that we will need for the next couple weeks on the islands. The current rate for Rupiah is 9200 per U.S. dollar. The clerk leafed through the $3500 of brand new $50 bills and inspected them carefully. I stood there smugly, knowing they were pristine and without any marks, folds or minor tears that would lower the exchange rate. She looked at me and casually announced that she would have to lower the exchange rate by 3% because the serial numbers all began with “CB.” I refused to cash them, even though I knew it was too late to go to a bank. I asked what other serial numbers were suspect of being counterfeit, and she said only ones beginning with “CB.” So back we went to the hotel and retrieved a similar amount of $100 bills, for which we got the 9200 rate.

I went to visit my friends at the Batu Arau Hotel, a beautiful structure that used to be a Dutch bank. It sits about a kilometer in from the sea on the north bank of the filthy river that serves as a harbor for fishing boats and surf charters. Christina Fowler and Chris run a surf charter and hotel/restaurant from there. There were a couple of people from Bali at the hotel, organizing relief efforts. Christina was overjoyed to see me and threw her arms around me, exclaiming something like “you warned us, you told us, it was just like you said!” She has written down her account of the tsunami surging up and down the river next to the hotel. No time to recount it all now, but there were many ebbs and flows over many, many hours. As best I can tell from her description, the crest to trough heights were as much as 2 to 3 meters. I will try to get a more precise account this morning. Bakosurtanal runs a tide gauge in Padang, so I imagine this will be an accurate account of the tsunami. Christina says that the dozens of boats on the river harbor rocked and swayed and tugged at their moorings, but that the sailors and fishermen were more entertained than worried. Flying fish and cuttlefish were brought in from the sea. Crabs were desperately running to the water line as the ebbs occurred and legions of leeches were inching up the wall of the concrete embankment to escape the sea water.

Christina’s partner, Chris, was on Siberut at the time of the earthquake and tsunami. Christina has his written accounts of what he saw and I have a copy of his pages. But I haven’t had time to study them yet. He reports days of “crazy water.”

Tulik and Myrna came by to see us later and have dinner with us at the hotel. Tulik is the Mentawai man in the photo with me in the New York Times article about a week ago. They’ll be coming by for breakfast Saturday morning, too. Not much more to report from them, except that Tulik continues to calm the islanders by telling them what to do in the event they feel a large earthquake. We are welcome to stay at his father’s new house in Saibi, if we wish.

Chris told me via satellite phone during dinner that relief work south of Simeuleu is proceeding well and that what is needed most now is fishing line and materials to repair fishing boats. Many relief agencies have saturated the areas south of the principal area of destruction. There are 5,000 people from the Meulaboh area settled in a refugee camp on Simeuleu island.

To my delight, when I arrived back at the hotel, Madi was there at the front desk. We were happy to see each other safe and sound, but he looked very stressed. He has the night shift tonight and isn’t off until 7 am. So we’ll talk in the morning.

I think that this will be my last chance to send a lengthy report, since I’ll be leaving for the small town of Muko Muko this afternoon, to catch our helicopter to the islands tomorrow morning. Very busy getting everything prepared this morning and afternoon! The boat leaves either tonight or tomorrow morning, to take our new GPS materials, our food and water, to Sikakap. We will meet it there tomorrow night.

Wide uplifted reef on westernmost tip of Simeuleu island. View is about to South.

Devastated village Ujung Sumbeu(?) on northwestern coast of Simeuleu island. Note large green tent. We stopped on reef here both to measure emergence and to offer relief supplies.

6:00 am, Sunday, January 9, Padang Hotel, Padang

Restless night here, anticipating our departure for the islands. Galetzka left the room at 2:00, to begin the six-hour drive down to Muko–Muko. Joining him are Felix (the technician/engineer from ACeS, the satellite telecom company we are working with), and Bambang. They will download the two GPS stations down there, and at about 11:00 will fly in two helicopters. Bambang to the Silabu station on the west coast of North Pagai, and John and Felix to the Perak Batu station on the east coast of South Pagai. We have two helicopters, because an Australian TV crew rented one to follow us around for a couple days. Now they don’t need the helicopter until the afternoon, because they are coming over in the speedboat of the Bupati (sort of the county supervisor).

The helicopter fuel for operating on the islands had not yet arrived by midnight last night, so Imam and the crew of our big boat (Km. Mutiara) will wait until it arrives before leaving the harbor for the 14-hour trip to Sikakap (a town of about 1500 people on North Pagai island). The big boat will be accompanying us up the island chain, carrying the fuel for the helicopter and providing our food, fresh water, and beds.

Danny and I leave at seven for Teluk Bungkus, the big harbor an hour to the south, where we’ll board the Bupati’s speedboat with the TV crew. We expect to arrive at Silabu by about 11:30 am, about the time that Bambang will arrive by helicopter.

Last night I took one of our educational posters over to the Batang Arau hotel at the harbor. Christina had told me she’d really like to have another one, now that the tsunami has happened. She had just spoken with Chris via satellite phone. He is distributing relief to the villages of the west side of Nias, who were hit very hard by the waves. He reports several hundred deaths and in some villages a nearly complete loss of their fishing fleets and, hence, livelihood. At his recommendation, Susi and Imam are buying a range of antibiotics (you can get them over-the-counter here) and fishing materials (nets, fish hooks, and line). Yesterday Susi was intent on buying dozens of pairs of ladies’ underwear to distribute. She was very concerned that they would be in short supply of this item. When I asked why not men’s she said men don’t need it as much! So anyway, I guess we’ll be distributing ladies’ underwear as part of our little relief effort. (The things I do in the course of trying to do science!)

At about 5:30 this morning the screeching from the minarets began here in town, calling the faithful to prayer. It is an indication that everything here in this very vulnerable city has gone back to the normal cycle of a normal day. The images of the disaster in Aceh continue to flood the local and national television channels, but people have by and large resumed their lives, as if nothing has happened. Yesterday, in the business center of the Bumi Minang Hotel, where I went to send my last e-mails, the girl who runs the office recognized me from the national TV interview a few days ago. She asked me if I was staying at the hotel. When I said no, she asked why. I just bit my lower lip gently, to keep from saying something that might frighten her. She saw my hesitation and sensed that I was not comfortable answering. She managed to drag out of me that I felt the hotel was too close to the water and too big of a structure for me to feel safe spending a lot of time there. Her playful mood became more somber. Later I learned from Danny that she had asked him the same questions and his answers had been the same as mine. I wonder how in the coming years we are going to approach the massive educational program that will be necessary to help the citizens of the large cities and villages along the coast figure out how to cope with their problem.

Islets along the northeast coast of South Pagai, between Sikakap and Perak Batu. We are flying south at this time.

Kids swarming the helicopter on the beach at Perak Batu, central east coast of South Pagai.

1:30 pm, Sikakap, Principal Town of the Pagai Islands

It took only about five hours to cross the Mentawai straits (the Bupati’s boat cruises at an amazing 20 knots, whereas our usual boat only goes about 10 knots or so). Many of our old friends greeted us as we walked through the town to reserve rooms in Pak Edi’s hotel (the Wisma Lestari) and find a restaurant for a quick lunch.

I was surprised to see no evidence of the tsunami here. A young guy with yellow plaster on his face, sitting on a tug boat hailed me. Oops, I’ve forgotten his name; maybe it’s Frizal, the guy in charge of the fisherman’s harbor. I think he said he was on the tugboat at the time and that the water poured over the wharf and into the grassy field between the wharf and the street. That suggests a surge about a meter above high tide. Our two most reliable friends told us what happened. Pak Edi says that the tsunami started with a withdrawal of the sea and rose up to the middle of the highest step of his house. I judge that to be about 2 meters above mean tide, but I’ll have to pin this down a little better tonight. [My later measurements show that the maximum height was about 70 cm above the sea level before the tsunami. The biggest surge came at about 3:00 pm here.] Devi (and her husband, Abeng) told me that the surge nearly filled the gully beside her house, but did not go into the street. I walked to the waterfront there and estimate that this would have been about a meter above the current water level. Pak Edi says the surge came during high tide. So, at first glance, it appears to me that the surge was only a meter or so, much less than in Padang.

Off to Silabu now, cruising west through the Sikakap Strait.

The Bupati's large and small boat in Teluk Bungus. We and the Australian 60-minutes crew took the small boat to Sikakap, South Pagai island.

5:50 pm, Cruising South Through Rough, Choppy Swells at Dusk from Silabu to Sikakap

We arrived late by speedboat at the mouth of the small mangrove-lined river that leads to Silabu. Only about an hour and a half to find a longboat to get us the 2 kilometers up the river, say hello to our friends, and meet Bambang and the helicopter. We arrived at the village at about 4:15 with the unusually high tide still rising over the grassy embankment. Every time I emerge from the mangroves to the little wooden homes, pig styes, and wharves of Silabu, I feel like I’ve entered the riverbank of The Wind in the Willows! So quaint and peaceful. Patroni and Suardi, two of the friends we made last August when we installed the GPS instrument, greeted us, along with a coterie of small kids and mothers.

We learned that the tsunami arrived at about 3:00 pm as a draining of the river. The river is probably about 2 meters deep and was drained completely dry. Five minutes later or so it filled again but did not top the banks. Ebbing and filling happened many times in the course of the day. The return of the water up the river brought an abundance of dead fish. I’m guessing that the draining of the fresh water into the bay killed the salt-water fish, which were then swept back in with the refilling of the river.

Everyone was all smiles as we walked along the concrete sidewalk through the town. Bambang had arrived an hour before in the helicopter and was downloading. Patroni walked with us up from the river to the GPS station, all the while telling us that all the villagers felt that our instrument had saved them from harm. We were thankful that they had such a good opinion of us and our instrument, but reminded them that if they ever feel a big earthquake they must immediately run to the high ground in the church yard, where the instrument is. Patroni reaffirmed that we and the instrument had been God–sent, just in time. Otherwise, how could both Bambang and we have arrived within an hour of each other—us by boat and him by helicopter?

We put the three guys in our group who were prone to seasickness on the helicopter for the return flight to Sikakap, while we went back to the boat for the return ride. Good decision—the chop made it a bit harrowing to get to the speedboat in the dugout, but here we are out in sea in a choppy 2–meter swell, motoring back to town. Just dove into a huge one, in fact, that bent the railing on the bow. We’re all a bit nervous.

Bambang Suwargadi, one of our Indonesian collaborators, in the helicopter.

1:20 pm, Monday, January 10, Wisma Lestari (a small hotel at the waterfront in Sikakap)

We have been frustrated by the choppy seas all morning, unable to leave safely for Perak Batu, a village on the east coast of South Pagai, where we have an instrument. Since our big boat was unable to cross from Padang yesterday, because of the choppy seas, we have only enough helicopter fuel to make one trip back and forth from Perak Batu. The TV crew needs to film us there, but we can’t take them and ourselves on the same trip. So an hour ago we decided to have their crew cross the strait in a boat, rent motorcycles, and drive as far as they can toward P.B. on the logging road that cuts southward along the ridgecrest of the island the road. Three of us will fly down and be deposited at Perak Batu, then the heli will pick up the motorcyclers nearby. Should be able to do everything before dark.

This noon, as I ate lunch at a small family restaurant, I watched the terrifying images of the tsunami surging through Banda Aceh, chock–full of cars and wood and other debris. I looked around at the dozen or so men, women, and children around me and started to tear up. Are they going to be the next victims, when the great Mentawai earthquake happens? It’s much easier to take if you don’t know the victims. If you have gotten to know many of them, and then they are swept away in a tsunami or crushed in a collapsing building, how do you cope? The grief of the people of Aceh must be immeasurable.

We have been telling people here to take three steps to deal with the possibilities here: 1) Don’t panic. It is unlikely that anything good will come from irrational behavior. And besides, we are here, so obviously we don’t think anything will happen in the immediate future. 2) Know how to flee. Figure out how you will flee to the hills if you feel a very strong earthquake. That will be easy for most of the residents here, because there is a tall hill with many paths right behind the town. 3) Figure out what to do about the long-term problem. Have community meetings to discuss whether to move the town to higher ground or to be willing to accept the losses and rebuild if the shaking and tsunami destroy the town.

Porites microatoll exposed and killed because of uplift during the 26 Dec 2004 earthquake.

10:20 pm, Tuesday, January 11, on the Boat in Sikakap Harbor

Yesterday we were able to get to the Perak Batu site and collect the data as planned, but barely got out before dark and before high tide overwashed the helicopter landing pad on the beach. Our friends in the small village were astonished and thrilled to have a helicopter land in front of their little town. Dozens of wonderful, cheering kids and mothers. But the men were off at work in the jungle and didn’t come back until about 4:30. They came back early because they saw the chopper land.

The seas are more calm today, so we will be able to depart for Tuapejat, our next site a few kilometers to the north. To conserve helicopter fuel we have decided to download that station by arriving by boat and to have the helicopter leapfrog on to the Sinyang-nyang site on a small island off the south coast of Siberut Island. The boat and helicopter will rendezvous at Malepet, a small harbor on the east coast of Siberut, tonight.

We are delayed this morning, because the local head (camat) and police chief have requested a meeting with us to discuss their concerns about a future earthquake and tsunami. The meeting was supposed to be at 8:00 am, but the ferryboat carrying them from Padang to Sikakap was delayed by the bad weather yesterday. If we don’t get out of here until 2:00 pm or so, we’ll suffer another day’s delay in our plans.

There are many stories to tell of meeting our friends in Perak Batu and here in Sikakap, but the time to write is just too short. Just one short note. Pak Edi has lived at the Wisma Lestari for 53 years. He says that high tides used to flood the courtyard about once a year. But since the Bengkulu earthquake in 2000, the high tides come into the courtyard every month. I wonder if this indicates merely that the man-made fill of coral rubble settled during the earthquake, or that there was some slow slip on the megathrust outboard of the islands! Too bad our GPS network had not yet been installed in 2000. Actually, Yehuda’s network could be resurveyed to see if anything odd happened up here at the time of the 2000 earthquake.

Our ship, the KM Mutiara leaving Sikakap harbor for Malepet.

Wednesday Morning, January 12, Tuapejat

The boat and helicopter left Sikakap harbor at the same time yesterday, as did the TV crew helicopter. They returned to Padang, via Muko Muko, and we headed north along the east coast of North Pagai, toward Tuapejat, a town of a couple thousand on the northern tip of Sipora island. We are now about two days behind the original schedule.

Bambang and I were to land at the Pulau Panjang GPS site, just a kilometer or so east of the town, and perform the first download of that station. But to our surprise, someone had stolen the receiver, batteries, and solar panel. We spent the afternoon reporting the loss to the Bupati’s office and then to the police who are in charge of Sipora island. We asked the mayor to bring the landowner to see us, so that we could find out the circumstances. Bambang stressed to the authorities that this was the sole instrument on Sipora, so that now we have no way of knowing what is going on beneath the island.

I couldn’t reach the boat by satellite phone this morning, but it is safe to assume that they arrived in Malepet (a harbor on the east coast of Siberut island, to our north) early this morning. The plan is that Bambang and I will download the Sinyang-nyang station off the south coast of Siberut, while the boat team downloads the Saibi station and installs the new telemetry.

We are sitting in a small café next to our little hotel. The complex of three buildings has been constructed right on the modern beach, as have dozens of homes and businesses here. I took a photo of one building that tilts toward the sea because the sand under it is being eroded away by the waves. Most of the town is less than a meter or so above sea level. In fact, we’ve been told before that during very high tides the main street floods, like Balboa Island in Newport Beach, actually.

The young couple who live in the room next to ours have three small children. I don’t see how they will escape if they are here when a tsunami strikes. It would be fairly easy to construct broad walkways perpendicular to the shoreline up onto the higher ground just behind the town.

Last night I took my usual stroll to clear my mind before turning in for the night. I walked the better part of a kilometer along the main drag, which parallels the beach. The stars were spectacularly bright and the sound of the small surf would have been calming under different circumstances. A group of about 15 fishermen sitting on a porch called me over to join them. They ranged in age from about 18 to 35, I’d guess. They knew that if they felt a big earthquake, they should run for the hills. They said they could get there within 30 minutes. I told them they might have only 15. They didn’t know what to do if they were on the water during a big earthquake. So I told them to try to get to deeper water.

Samsir (mechanic), Dayat (pilot), Busral (Deputy Police Chief (PolSek), Bambang and another policeman, just before departure from Tuapejat to Nyangnyang.

10:00 am, Sinyang-nyang Site

We left the Bupati’s office at Tuapejat about an hour and a half ago, then flew across the Sipora Strait to Nyangnyang island. What a beautiful site this is! High on a hill, overlooking the archipelago of small islands off the southeast coast of Siberut island. We were delighted to see that the instruments are intact and have been recording since we left them in September. We’ll finish the download of data at about noon.

A young woman and two young boys walked up to meet us a few minutes after we landed. She is Thaddeus’s daughter. He owned land in this area and was killed by three men last December, because he would not sell the land to someone who wanted to build a resort here. The men are now in custody. The owner of the particular piece of land that the instrument is on is Petros. Bambang will give the maintenance money to Martena to give to Petros.

Two guys in their late 20s and 30s came up toward the end of the three-hour download. They said that there had been oscillations of the sea from about 11:00 am to about 6:00 pm on the day of the earthquake. They say it was low tide when it began, and that the first surge came up about a meter, to near the normal high-tide mark. They didn’t know whether the first effect was a withdrawal or a rise of the sea.

Nyangnyang GPS station. View about to northeast.

Helicopter, instrument and open instrument box at the Nyangnyang site.

10:00 am, Thursday, January 13, En Route from Lebuan Bajou to Tello, on the Big Boat

Bambang and I flew from the Nyangnyang site over the large north-south bay of southern Siberut island late yesterday morning en route to Malepet, on the east coast of Siberut. It was nearly low tide during our transit, so we could inspect the intertidal zone en route. Fields of coral microatolls are abundant in the southern third of the bay but the northern two-thirds is a mudflat.

Our big boat had left two 50-gallon barrels of fuel in a soccer field near Malepet, so that we could refuel. We left the helicopter running during refueling, and a large crowd from the community gathered around. I recognized one long-haired character who came up to greet me. He is named Su, and we met here a few years ago, when we were in the area collecting coral samples. He is about 27 or so, and still looking for work. I forgot to ask about the tsunami there.

Continuing north, we flew over vast tracts of virgin jungle, with the double canopy of high, white-barked dipterocarps and understory of shorter trees. What a joy to see that so much of the forest here has not been logged by the big timber companies. At least a small part of the Mentawai islands might yet remain pristine.

We overtook our big boat just 10 km or so south of our next stop, at Muarasaibi. Our MSAI station is on a hill overlooking this village of several hundred Mentawai people. We’ve become good friends with many of them, since we first installed the GPS station there. David Satoko is the owner of the land on which the station sits, and he takes extraordinarily good care of the site, keeping the weeds down. He has even built a little bamboo shelter for us during our downloads.

Last August, our friend, Tulik, who is from Saibi, showed Catharine Stebbins and me the evidence for coastal erosion and submergence in the water in front of the village. I took good aerial shots of the remains of the boardwalk that used to be behind the beach, in the swamp and the freshwater spring that now sits seaward of the beach.

We landed in the soccer field, surrounded by beautiful little wooden homes, including the mayor’s (Mr. Surkino). After a few minutes of greeting on the mayor’s porch, Bambang walked up the station. I went up with my retinue a little later. The receiver refused to download properly, so we waited for John to arrive by our small aluminum boat. From the station, we could see that his group was struggling to find the mouth of the river on the delta, a few hundred meters offshore. John couldn’t get the receiver to download properly, either, so I decided that we would swap it out with a new one. I did not want to leave the troubled receiver there at the site, even though it was recording properly, because that would mean that we had no new data, covering the earthquake and post-seismic period. So we went out in our friend Kisman’s longboat to the big boat to get a new receiver. This meant, of course, that we would have one less receiver to install on the islands or mainland near the Dec 26th rupture.

Danny and John stayed on overnight at Muarasaibi, but the rest of us boarded our big boat and continued its slow trek to the north. We stayed the night in the harbor of Lebuan Bajau, on the northeastern tip of Siberut island. We were pleased to hear from John later in the night that he had, after all, been successful in downloading the Saibi station receiver, so there would be no need to use the new receiver there.

We are now on our way across the wide strait between Siberut island and the Batu islands to the north. I’m hoping that we can reach Tello by early afternoon, so that we can download the station there, while Danny and John are downloading the Air Bangis station, on the coast near the equator, and the Bais station, just east of Tello. We plan to rendezvous in Tello, just south of the equator, tonight.

Our logistics issues (fuel for boat and helicopter, and permissions to go into the stricken area) are getting resolved, one by one. Thanks to ACeS and Adi Adiwoso for satellite phones! And thanks to Christina and Chris at the Batang Arau hotel in Padang, and to the LIPI staff in Jakarta and Bandung for going to bat for us on all of this. Bambang just learned that we now have a letter from the military that gives us permission to use some of their helicopter fuel.

Bambang is resting below deck now; he suffers from chronic seasickness. I’m feeling a bit nauseated, myself, so I think I’ll lie down for a bit, also.

12:56 pm. A half hour ago, the boat stopped and the captain told us that the engine has been leaking oil for the past day and that now there is too little to safely continue on to Tello. So we are dead in the water here just inside the south entrance to the long narrow strait between Tanabala and Tanamasa islands. We can’t reach John and Danny via satellite phone to ask them to fly oil to us, so we have sent Bambang and two of the boatmen in our dingy the 45 km to Tello, where they will buy enough oil to get the boat to Tello. It will be a four–hour round–trip, so the boatmen will probably not be back until about 6:00 pm. Bambang will stay in Tello, to begin to work out other logistical details of the trip.

9:47 pm. The dinghy has just arrived back from Tello with two 5–gallon containers of oil. Hallelujah, we might make it to Tello yet tonight, if the captain is willing to navigate the straits by the light of the stars. Otherwise, it’s four hours beginning at first light. John and Danny got the two stations at Air Bangis and Bais downloaded today, so we have only Tello and Simuk to download here on the islands. Sikuai and Jambi we can do later in the month, after we’ve finished our business in the earthquake region.

The delta at Muarasaibi, central east coast of Siberut island, near low tide.

Close-up of posts from old boardwalk that was in the marsh when Tulik was young and is now in front of the beach.

Local men loading our helicopter fuel drums onto a pickup for transport to the airport. Riding in the back of the pickup with them to the airport, they told me the water level in the harbor is now about 50 cm higher than before the earthquake.

8:30 am, Friday, January 14, En Route to Tello on the Big Boat

We waited until dawn to resume our trek through the strait and on to Tello; there are too many shallow spots and narrow slots to travel through on a moonless night. I slept in John’s hammock on the top of the boat, since he was in Tello last night with Danny and Bambang. They reported by phone at 11:00 last night that Tello is astir with fears and rumors of another earthquake and tsunami. They spend the late afternoon and evening talking, talking, and talking to individuals and groups about their concerns. Danny confirms that the tsunami there surged into the main street, but that little damage was done. He took notes on the tsunamis at Bais and Air Bangis, based upon eyewitness accounts.

Danny says reports in Tello from Simuk island, the farthest out and most exposed to the tsunamis, are that they also suffered no loss of life from the tsunamis. We breathe a sigh of relief, now, believing that none of our friends appear to have lost their life or property—this time.

I called Heather last night at midnight (9:00 am at Caltech) and asked her to wire-transfer more money from our accounts there to the helicopter company. We’ll need this to reconnoiter Simeuleu and Nias. I doubt that we’ll have time to get to the mainland coast before I leave; too many logistical snafus this first week on the islands.

Town on promontory between Air Bangis and Padang. Is this a Sirombu disaster waiting to happen?

8:00 am, Saturday, January 15, Tello, Just South of the Equator

We made two trips out to Simuk island yesterday; first John and Imam left to begin downloading data and then Bambang and I went to measure tsunami heights and to talk to the villagers there. The big boat stayed behind in Tello to have its engine repaired—a task that the captain judged would take about three hours.

Simuk is a vast flat island, roughly elliptical in shape, but with three blunt peninsulas jutting meekly to the west into the Indian Ocean. It is the most remote of all our islands, farthest from the mainland coast of Sumatra. Huge tsunamis reportedly overwashed much of the island after the giant earthquake of 1861, caused by rupture of the megathrust under Nias island, just to the north. Flying over the island, one sees vast tracts of coconut plantation, with a few small wisps of smoke rising from burning debris. The highest part of the island is a soccer-field-sized flat hilltop about 20 meters above sea level. That is the location we chose a couple years ago for our GPS station.

When John and Imam flew over the Simuk GPS site, they found that the large cleared area around the instrument was covered with temporary shelters. Many families had fled there after the tsunamis of December 26th and were still encamped there. One was just a meter or so from the antenna. Last August, we had actually advised them to go to high ground in the event of a large earthquake, but we had no thought that they would encamp there for weeks!

The couple of hundred “refugees” greeted us upon our arrival on the flat hilltop. We held an impromptu meeting with them there on the site, because they were all very concerned about a rumor that had spread among them; there was to be another large tsunami tomorrow, January 15th. To keep order, one leader among them asked for questions from them, which I answered and Bambang translated.

Then, while John and Imam downloaded data, Bambang and I and a dozen or so children took the path down the cliff and through the couple kilometers of coconut plantations to the village by the sea. We spent about an hour in an impromptu meeting with a few dozen more villagers, organized by Pak Emir (a friend of ours and prominent citizen of Tello, who is in charge of the health services in the area). Everywhere, people wanted copies of our brochure, so they could understand better the earthquakes and tsunamis. Many intelligent questions from people who knew they were at risk from any tsunami that might be larger than the one that washed through about half of their village just three weeks ago. Pak Emir summarized the timing of the tsunami: four ebbs and flows between about 9:00 am (1½ hours after they felt the earthquake) and 5:00 pm, with the ebbs preceding the flows.

Dozens of us then walked down the village street to the beach and found a guy who lived near the beach and was there on the day of the tsunami. Although the waves washed about 100 meters into the village, the evidence for the flood is scant and unimpressive. Based upon the guy’s observations, we measured the tsunami height, from sea level just before the tsunami to the crest of the highest wave: 3.2 meters! The depth of the deepest trough was about 2 meters.

We arrived back in Tello in the late afternoon and found that the boat engine cannot be repaired here in Tello! To make matters worse, all of the new GPS receivers that we were planning to install to the north have now been used to replace defective receivers within our existing network.

So last night we were “dead in the water” again, but with a finality that was pretty depressing, albeit in a beautiful little town and a safe harbor. The boat will have to be towed back to Padang for the repair; the needed parts are not available here. Within the hour, we hatched a new plan: We will split into a GPS crew that will head back to Padang on Monday, the 17th, and a reconnaissance team that will continue north with the helicopter to survey Nias and Simeuleu. We rented a cargo boat here in Tello to carry our helicopter fuel, food, and relief supplies, first to Nias and then to Simeuleu. Imam and Danny and I will go north with the new boat (the Rinjani) and helicopter. John and Bambang and Felix will store all the GPS gear here in Tello and then return to Padang to await the shipment of four new receivers from the U.S. In the meantime they will send the GPS data we have collected back to the U.S. for processing. Danny and I will have the 15th through the 18th to reconnoiter the islands to the north for evidence of uplift or submergence (and to document tsunami heights, as time permits).

Danny and I now await the passage of a large black rain squall that has moved in from the north, before we can take off! I have learned in Indonesia that patience is a virtue.

Danny Natawidjaja in the helicopter.

The helicopter, the people and the antenna at the Simuk island GPS station.

Danny photographing eager villagers on the new reef at Lhokmakfur.

10:30 am, Sunday, January 16, Sinabang, Capital of Simeuleu Island

Midday yesterday we flew across the equator to Telukdalam, on the southern coast of Nias island and near Lagundri bay, a world-famous spot for surfing. Chris and Christina’s boat from Padang had, in fact, dropped off five barrels of helicopter fuel for us, but we could not find it at the wharf. Anticipating disaster, we called Chris in Padang, who assured us that it had arrived the previous night. He gave me directions to his agent, Ama Pipir’s house, where it would have been stored. Just happened to meet Johny, one of Ama Pipir’s nephews, as I was wondering how to get to there. He took me on his motorcycle to Ama’s house, where it became clear that I had nothing to worry about. Ama’s wife brought me five very delicious mangoes—I ate one, and had a taste of what it must be like in heaven. Saved the rest for the next few days.

Johny and Ama Pipir’s family told me that they felt the earthquake Sunday at about 8:30 and said that it lasted about five minutes. The first regression of the water began at 10:00 am. The water did not come back up until 11:30 am. Then there were many oscillations, which didn’t stop until nighttime. The biggest surge was at two o’clock in the afternoon.

We made it to our final rendezvous with the Austalian 60 Minutes crew at Sirombu, halfway up the west coast of Nias. The tsunami damage there was horrific. I felt a bit silly landing in a helicopter, saying a few hellos to the villagers who greeted us and then immediately starting to work with the film crew. Seemed a bit crass, actually, in the face of all the suffering going on there. I was thankful that we only spent a half hour interviewing and filming, before interviewing villagers and making observations of the tsunami height. About 4.5 meters. Only eight villagers died here, though, because the big wave hit hours after the first ones arrived, giving all the residents hours of advance notice.

Yamo, a resident of Sirombu, who was in Gunungsitoli at the time of the disaster, says that his family member, Fauzi, rode out the tsunami surge in the second floor of his home and is a reliable eyewitness. The big wave came at 4:00 pm and came from the south, not the north. This must mean that the tsunami reflected off of eastern India and Sri Lanka and came back to the Indonesian islands.

We left Sirombu flying north, reconnoitering the coast all the way to the northern edge of the island. One particularly impressive sight was an entire grove of dead coconut palms sitting out on the reef, seaward of the beach. These obviously had died some time ago, not as a result of the tsunami. They show that the west coast of Nias, like the islands we have been studying farther south, have been sinking during the past several decades. The islands are like a spring board, storing strain for the day when the megathrust below gives way and they spring suddenly back up, producing a great earthquake and tsunami.

We spent the night in the capital city of Nias, Gunungsitoli, on the central eastern coast of the island. Our modest rooms cost us just $5 each! In the evening, I heard amazing stories from the three guys from Telukdalam who had driven our fuel by truck to G.Sitoli. Alimin is a 52–year–old guy who lives on the waterfront in T.Dalam, in the silver-roofed house in the photo on the next page. He was in his house when the water rose into it. He says the water rose 1.3 meters (to his chest) above the floor in his house. The floor of his house is 2.5 meters above low tide. This suggests that the amplitude of the highest surge was about 3.8 meters. During the recessions of the sea, the floor of the bay was completely high and dry out to 50 meters from the shore. He and Ama Pipir’s son, Handy, estimate the drop was 6 to 7 meters below sea level! At the time of the tsunami, the sea was near low tide. Handy and his friend here, Herman, were on Ama Pipir’s squid boat when the tsunami happened. The boat sank down with the water and came to rest on rocks. They scrambled out and made it to shore before the next surge.

Our new fuel-supply boat arrived at about 4:00 am, and loaded on the extra fuel barrel that had been delivered by truck from Telukdalam the night before. They took off again for here, Sinabang, at about 11 am, we think. It will be a 20-hour trip at about 7 miles per hour for them from G.Sitoli to Sinabang. The same trip took us just 1.5 hours late this morning.

We were welcomed warmly by the Bupati of Simeuleu, Durmili. His assistant, Riswan, was waiting for us at the airport when we landed. We were spirited away to the Bupati’s home in Sinabang, where we met a crowd of foreigners with other objectives—medical, media, etc.

Went on a car caravan with the whole crowd, led by the Bupati, to view tsunami damage on the southern part of the southwestern coast. Measured heights of about 2.5 meters. All stories still say that the first indication was a recession of the sea. Also of interest to Danny and me was the evidence for small amounts of permanent submergence in these towns. Areas that used to be dry now have up to 30 cm of standing water in them. Local residents insist that the beaches have eroded ten meters or so since the tsunami.

We heard from the Bupati that word has come from the northern coast that the coral reef there is about a meter out of the water. This is almost precisely what Danny and I had been guessing would be the case. We will fly there tomorrow morning to see if the reports are true and, if so, to make some measurements. If the northern part of the island has risen, it means that the southern end of the great megathrust rupture that caused the earthquake is under the island.

At the end of our trip, back at the Bupati’s home, we learned from one of the staff that Pak Riswan had lost all four of his children in the tsunami in Banda Aceh, the provincial capital. He was such a stoic all afternoon long. One would never have suspected that the tragedy was for him also a very personal one.

A few minutes ago, about 10:45, dozens of people began running up the street past my second-story room, away from the wharf, yelling out to one another. Turns out the rumor of a tsunami had caused them to flee. It didn’t even occur to me that that was the cause, since I hadn’t felt an earthquake. People are clearly on edge here and on Nias. So many people ask us if another earthquake and tsunami are coming.

Telukdalam town, on west side of bay. According to an eyewitness living in the silver-roofed house at bottom right, the highest water surge here was about 3.8 meters.

Aerial oblique view of part of Sirombu. View across the isthmus, looking approximately north. Only eight people died here, because the big wave happened many hours after the first one.

Grid of submerging coconut palms on promontory of northwestern coast of Nias.

Detail of tsunami damage in a town along the southwest coast of Simeuleu.

Porites microatoll uplifted about 90 cm during Dec 26, 2005 earthquake on reef near town of Ujung Salang.

8:46 am, Thursday, January 20, En route from Padang to Jakarta and Singapore

Monday and Tuesday on Simeuleu island were extraordinary, both scientifically and emotionally. On Monday we flew along the southwestern coast, past a score or more fallen bridges and as many coastal villages, devastated by the tsunami. Near where the island doubles its width we began to see evidence of what looked like an extremely low tide—barren, pale tan ribbons of coral reef paralleling the coast and extending a hundred meters and more from the beaches to the waterline.

During our first circling of one of these reef ribbons, we saw striking evidence of emergence—pristine pancake-shaped heads of Porites coral, well above current water level. We landed on the 200-meter wide former shallow reef platform, about half-way between the former sandy beach and the new shoreline. Before we could shut down the engine, a hundred or more children and adults swarmed out onto the reef from the trees. We immediately split ourselves into a science team and a relief team; Danny and I began to inspect the corals, while Dayat and Samsir (our pilot and mechanic) began to talk to the villagers and distribute the materials we had brought along as relief aid—clothing, powdered milk, hammers, and fishing equipment, mostly.

Even though Danny and I have for the past several years been studying ancient evidence of the slow sinking and fast emergence of the Sumatran coral reefs, we were astonished to find ourselves walking through a pristine marine ecosystem, missing only its multitude of colors, its fish, and its water. Corals of every shape and size rested lifeless on the reef platform—branching corals, massive corals, staghorn corals, fire corals, brain corals, whorls, fans. And here and there a poor crab. Even though the tsunami had raged across the reef, there was scant evidence of breakage of the delicate whorls and dendritic corals that crunched beneath our feet. But a fishing boat in the trees beyond the shoreline and overturned two-ton umbrella-shaped Porites heads were testimony to the power of the tsunami. The scene was the marine equivalent of a village on the flank of a volcano after the passage of a nuee ardente—life quick-frozen in place at the moment of death.

Like us, the villagers quickly segregated into two groups. Most of the adults surrounded Dayat and Samsir, but many of the barefoot children came racing on to Danny and me. Smiling, cheering, boisterous young boys and girls, eager to play with us and to watch what we were doing. We had noticed as we circled the reef that their village, Ujung Salang, had been completely washed over by the tsunami. Hardly a building remained. Yet, there was no trace of sadness in their beautiful faces. I have no idea where they are living now—on higher ground in the forest, I imagine. They were eager to be in the pictures I was taking. In fact, I had to coax them to the sides of the images, so that I could see the corals. I have one picture with several kids standing on top of a pancake-shaped coral head. They are standing at what used to be lowest low tide of the year. At the time of our visit, the water level was a meter lower.

We estimate the emergence here to be nearly a meter and a half. To produce so much uplift, the block above the gently northeast-dipping megathrust, 25 km or so beneath the reefs, must have slipped about 10 meters toward the southwest.

We hopscotched our way farther north for the rest of the afternoon, stopping only occasionally to make an additional measurement and diverting around rain storms. A systematic, detailed survey will have to wait until we can return, hopefully in a few months. Newly emerged reef ribbons were everywhere along the northern coast. The emergence had doubled the diameter of some of the smaller islets. And along most of these coastlines were old stands of decayed coconut palms and other trees out on the reef, seaward of the old beach—testaments to the fact that the land had been sinking slowly in the decades before the earthquake. In the complexly embayed coastline of the northern coast, muddy flats surrounded by mangrove forest have emerged above water also. Some of these have muddy brown rectangular fields on them. I think these are very old rice paddies that slowly submerged into the intertidal zone or below in the decades prior to the earthquake. And now they are back above high tide, ready for cultivation again! Some villagers have, in fact, asked us if the water will return and submerge the newly dried reef and mud flats soon. We tell them with confidence that submergence of these new lands will not occur soon. It will take more than a hundred years for the water to return to its levels on the day before the earthquake.

On Tuesday it was more of the same. We filled some of the gaps between our measurement sites and reconnoitered the northeastern coast. The former lowest low–tide level is now at least 25 centimeters above water. So the island tilted coseismically both from northwest to southeast and from southwest to northeast. The pattern and magnitude of uplift is strikingly similar to what we know happened to the south in the Mentawai islands during the M 8.7 earthquake of 1833. The half-hour flight back south to Sinabang took us over vast tracts of virgin forest, full of tall, white-trunked Dipterocarps towering over the lush understory. Inspiring flight, tempered only by the fact that both of us were a bit uncomfortable in our pants, soaked from our wading in shallow water.

We briefed Bupati Darmili on our findings late Tuesday evening, back in Sinabang. We presented him with two gifts from his own island – a small, bulbous, bleached-white head of pristine Goniastrea retiformis (a honeycomb-like coral) from one of the dead reefs and a CD with many of our photographs. He is a gracious and thoughtful man, who seems intent on understanding what has happened, so that he can make good decisions about what to do to help his island recover. We mentioned our interest in establishing a couple of continuous GPS stations on the island, to monitor the “healing” of the earthquake wound. He said he would welcome our return.

Yesterday, Wednesday, we all left Simeuleu. Danny and Imam flew to Medan, the capital of North Sumatra, on a small commercial airplane, while I flew with the helicopter crew back to Padang. Passing low over the virgin forests and rice paddies of southern Simeuleu, it occurred to me that this might well be the most beautiful of all the islands in the chain. We landed twice along the five-hour journey to refuel, at Gunungsitoli and Air Bangis, where we had made sure to stash barrels of fuel for the return flight. At Air Bangis, a town almost right on the equator, an official came to see me while I was waiting in an airy little hotel lobby for the refueling to be completed. He asked for advice about what to do to protect the city. His concerns are warranted: Passing along the coast of mainland Sumatra, between the equator and Padang, we saw ample evidence of the possibility of a repetition of the disaster of December 26th. As along the west coast of Aceh, North and West Sumatrans have built many of their villages, towns, and cities right on the coast, directly east of the source of giant earthquakes. In some cases, towns and villages sit on barrier beaches, between the sea and long estuaries. Without the construction of bridges across the estuaries in the coming years, there will be no safe place for the townspeople to flee in the 15 minutes or so between the earthquake and the tsunami surges.

Uplifted reefs on mainland coast and island near town of Ujung Salang, devasted by an unusally long surge onto land.

An overturned umbrella-shaped Porites head. Kids shown for scale and for fun.

The uplifted reef near Ujung Salang.

Flooded rice paddies near northern tip of Simeuleu island. Could these be coseismically emergent paddies that were slowly flooded in the years before the earthquake?

The GPS station near Air Bangis, west coast of Sumatra near the equator. The burning of the grass around the equipment occurred just a couple days before. Air Bangis is in the background.

Discover Magazine printed the blog of Kerry Sieh and John Galetzka's return to Sumatra in mid-May of 2005.

Last updated: Mon Oct 08 09:54:59 -0700 2007

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