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Earthquake Early Warning |
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Earthquake Early Warning
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. As warning times 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.
CISN ShakeAlert - An Earthquake Early Warning Demonstration System for California
Scientists and engineers at the California Institute of Technology (Caltech), UC Berkeley, the Swiss Federal Institute of Technology (ETH), and the University of Southern California (USC) started in 2007 to develop and implement an earthquake early warning (EEW) demonstration system for California, called CISN ShakeAlert (Bӧse et al., 2012). The purpose of CISN ShakeAlert is to demonstrate the feasibility of EEW in California and to show how a future operational warning system based on the California Integrated Seismic Network (CISN) could possibly look like.
CISN ShakeAlert is a hybrid system that combines the outputs from three algorithms implemented in parallel, τc-Pd Onsite (Kanamori, 2005; Wu et al., 2007; Bӧse et al., 2009), Virtual Seismologist (Cua et al., 2009), and ElarmS (Allen et al., 2009), to calculate and report at a given time the most probable earthquake magnitude and location; a UserDisplay (UD) receives the alert messages in real-time, calculates the expected local shaking intensity (MMI), and displays the information on a map (Bӧse et al., 2012). The alerts are 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., Allen, R., Brown, H., Cua, G., Fischer, M., Hauksson, E., Heaton, T., Hellweg, M., Liukis, M., Neuhauser, D., Maechling, P. & CISN EEW Group, 2012: CISN ShakeAlert: An Earthquake Early Warning Demonstration System for California, in: Early Warning for Geological Disasters - Scientific concepts and current practice. Bӧse, M. and T.H. Heaton, 2010: Probabilistic Prediction of Rupture Length, Slip and Seismic Ground Motions for an Ongoing Rupture: Implications for Early Warning for Large Earthquakes, Geophys. J. Int., 183(2), pp. 1014-1030, doi: 10.1111/j.1365-246X.2010.04774.x link Bӧse, M., T.H. Heaton, and E. Hauksson, 2012: Real-time Finite Fault Rupture Detector (FinDer) for Large Earthquakes, Geophys. J. Int., 191(2), pp. 803-812, doi: 10.1111/j.1365-246X.2012.05657.x link 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. Wu, Y.-M., H. Kanamori, R.M. Allen, and E. Hauksson, 2007. Determination of earthquake early warning parameters, τc and Pd, for southern California, Geophys. J. Int. 170 711-717, doi: 10.1111/j.1365-246X.2007.03430.x.
PreSEIS: Using Artificial Neural Networks for Earthquake Early Warning
The major challenge in the development of EEW systems is the achievement of 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 later successfully tested within the European SAFER-project for earthquakes in southern California (Kӧhler et al., 2009) and EWS Transport (Fraunhofer Institute). Bӧse et al., (2012) modified the approach to requiring seismic information from a single sensor only (PreSEIS Onsite).
References: Bӧse, M., T.H. Heaton, and E. Hauksson, 2012: Earthquake Early Warning Using Data from Single Broadband or Strong-motion Sensor, Bull. Seism. Soc. Am., 102(2), pp. 738-750, April 2012, doi: 10.1785/0120110152 link 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. link 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
Earthquake Early Warning for Bucharest, Romania
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) demonstrates 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.
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Earthquake early warning. |
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Last up-date: 12/13/2012 |
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Maren Bӧse, Phd Senior ReseaRch Fellow |
