Earthquake Early Warning

Maren Bӧse, PHD

Earthquake early warning (EEW) systems make use of differences in the propagation speed of seismic and electromagnetic waves and issue warnings, if necessary, to potential users before strong shaking at these sites occurs. The maximal warning time of an EEW system is generally defined as the time span between the P-wave detection at the first triggered EEW sensor and the arrival of high-amplitude S- or surface waves at the user site. As these time periods usually are extremely short, EEW systems must recognize the severity of expected ground motions within a few seconds. Based on this information, suitable actions for the damage reduction can be triggered and executed. Possible measures are, e.g., the automatic slow-down of rapid-transit vehicles and high-speed trains to avoid accidents, the automatic shutdown of pipelines and gas lines to minimize fire hazards, the automatic shutdown of manufacturing operations to decrease potential damage to equipment, the automatic saving of vital computer information to avoid losses of data, and actions that support the semi-active control of structures to prevent building collapses.

References:

Allen, R.M., Gasparini, P., Kamigaichi, O. and M. Bӧse, 2009: The status of earthquake early warning around the world: an introductory overview, Seism. Res. Lett., 80(5), pp. 682-693, doi: 10.1785/gssrl.80.5.682. link.

Earthquake early warning.

PreSEIS: Earthquake Early Warning for Istanbul, Turkey

Earthquake Early Warning in California

Earthquake Early Warning for Bucharest, Romania

The major challenge in the development of EEW systems is the achievement of a robust performance at largest possible warning time. I have developed a new method for EEW (called PreSEIS) that is as quick as methods that are based on single station observations and, at the same time, shows a higher robustness than most other approaches. At regular time steps after the triggering of the first EEW sensor, PreSEIS estimates the most likely source parameters of an earthquake using the available information on ground motions at different sensors in a seismic network. The approach is based on two-layer feed-forward neural networks to estimate the earthquake hypocenter location, its moment magnitude, and the expansion of the evolving seismic rupture (Bӧse, 2006; Bӧse et al., 2008).

Bӧse et al., (2008) show that the uncertainties of the estimated parameters (and thus of the warnings) decrease with time. This reveals a trade-off between the reliability of the warning on the one hand, and the remaining warning time on the other hand. The ongoing up-date of predictions with time allows PreSEIS to handle complex ruptures, in which the largest fault slips do not occur close to the point of rupture initiation.

PreSEIS has been developed and tested using the example of the Istanbul Earthquake Rapid Response and Early Warning System (Bӧse et al., 2008) and is currently tested within the European SAFER-project for earthquakes in southern California (Kӧhler et al., 2009).

References:

Bӧse, M., Wenzel, F., and M. Erdik, 2008: PreSEIS: A Neural Network based Approach to Earthquake Early Warning for Finite Faults, Bull. Seism. Soc. Am., Vol. 98, No. 1, pp. 366-382; doi: 10.1785/0120070002. l ink

Bӧse, M., 2006: Earthquake Early Warning for Istanbul using Artificial Neural Networks, PhD thesis, 181 pp., Karlsruhe University, Germany, 10 Nov. link

Kӧhler, N., Cua, G., Wenzel, F., and M. Bӧse: Rapid Source Parameter Estimations of Southern California Earthquakes Using PreSEIS, Seism.. Res. Lett.., Seism. Res. Lett. 80 (5), pp. 748-754, doi: 10.1785/gssrl.80.5.748. link

Over the past three years the California Integrated Seismic Network (CISN) has tested the real-time performance of three algorithms for providing earthquake early warnings in California: the single-sensor based τ_c-P_d on-site and the network-based (2) ElarmS, and the (3) Virtual Seismologist (VS) algorithms. The algorithms have successfully detected many earthquakes and in some cases predicted the peak ground shaking a few seconds before it was felt. In the next three years we plan to migrate from three semi-parallel processing threads to a single integrated system, called CISN ShakeAlert. This prototype thread will provide a continuum of earthquake alert information ranging from the earliest shaking predictions based on P-wave detections at the epicenter, through S-wave detection and integration into warnings, to peak shaking observations at the epicenter and integration into warnings at greater distances. The alerts will be passed to a small group of collaborating users to develop early warning procedures and formats that could be used in a complete end-to-end prototype warning system in the future.

References:

Allen, R. M. (2007). The ElarmS earthquake early warning methodology and its application across California, in "Earthquake Early Warning Systems", P. Gasparini, G. Manfredi, J. Zschau (Eds.), 21-44, Springer, ISBN-13 978-3-540-72240-3.

Bӧse, M., Hauksson, E., Solanki, K., Kanamori, H., Wu, Y.-M., and Heaton, T.H., 2009: A New Trigger Criterion for Improved Real-time Performance of On-site Earthquake Early Warning in Southern California, Bull. Seism. Soc. Am., 99, 2A, pp. 897-905, doi: 10.1785/0120080034. link

Bӧse, M., Hauksson, E., Solanki, K., Kanamori, H., and T.H. Heaton:, 2009 Real-Time Testing of the On-site Warning Algorithm in Southern California and Its Performance During the July 29 2008 Mw5.4 Chino Hills Earthquake, Geophys. Res. Lett.., Vol. 36, L00B03, doi:10.1029/2008GL036366. link

Cua, G., and T. Heaton, 2007. The Virtual Seismologist (VS) method: a Bayesian approach to earthquake early warning, in "Earthquake Early Warning Systems", P. Gasparini, G. Manfredi, J. Zschau (Eds.), 85-132, Springer, ISBN-13 978-3-540-72240-3.

Hauksson, E., K. Solanki, D. Given, P. Maechling, D. Oppenheimer, D. Neuhauser, and P. Hellweg, 2006. Implementation of Real-Time Testing of Earthquake Early Warning Algorithms: Using the California Integrated Seismic Network (CISN) Infrastructure as a Test Bed (abstract), Seismol. Soc. Am. Annual Meeting, April 18-22, 2006, San Francisco CA.

Wu, Y.-M., H. Kanamori, R.M. Allen, and E. Hauksson, 2007. Determination of earthquake early warning parameters, τ_c and P_d, for southern California, Geophys. J. Int. 170 711-717, doi: 10.1111/j.1365-246X.2007.03430.x.

The accumulation of strong earthquakes with resembling source mechanisms in the Romanian Vrancea zone, SE Carpathians, allows for designing a simple, cheep and robust earthquake early warning (EEW) system for Bucharest with leading times of about 25 s. A previously established scaling relation for EEW predicts in the range from 1-2 s a ten times higher ground motion amplitude in Bucharest than the maximum P-wave acceleration measured in the epicentral area (Wenzel et al., 1999). Using additional weak and strong motion data, Bӧse et al. (2007) find that ground shaking in Bucharest is generally overestimated by this relation by a factor of two. However, the predicted amplitudes are within the 95% confidence interval of the revised relation. Additional predictive laws for EEW are determined for different ground motion parameters, including spectral acceleration, seismic intensity, and peak ground velocity (PGV). The application of the scaling relations to the October 27, 2004 Vrancea earthquake (Mw = 6.0) supports the feasibility of the approach for EEW in Romania.

References:

Bӧse, M., C. Ionescu, and F. Wenzel, 2007: Earthquake early warning for Bucharest, Romania: Novel and revised scaling relations, Geophys. Res. Lett., 34, L07302, doi:10.1029/2007GL029396. link

Wenzel, F., M. Oncescu, M. Baur, and F. Fiedrich, 1999. An early warning system for Bucharest, Seismol. Res. Lett., 70(2), 161–169.

Bӧse, M., Sokolov, V., and F. Wenzel, 2009: Shake Map Methodology for intermediate-depth Vrancea (Romania) Earthquakes Earthquake Spectra, Vol. 25, No. 3, pp. 1-x, doi: 10.1193/1.3148882.

Last up-date:

1/5/2011