Predictability study on the aftershock sequence following the 2011 Tohoku-Oki, Japan, earthquake: first results

SUMMARY Although no deterministic and reliable earthquake precursor is known to date, we are steadily gaining insight into probabilistic forecasting that draws on space–time characteristics of earthquake clustering. Clustering-based models aiming to forecast earthquakes within the next 24 hours are under test in the global project ‘Collaboratory for the Study of Earthquake Predictability’ (CSEP). The 2011 March 11 magnitude 9.0 Tohoku-Oki earthquake in Japan provides a unique opportunity to test the existing 1-day CSEP models against its unprecedentedly active aftershock sequence. The original CSEP experiment performs tests after the catalogue is finalized to avoid bias due to poor data quality. However, this study differs from this tradition and uses the preliminary catalogue revised and updated by the Japan Meteorological Agency (JMA), which is often incomplete but is immediately available. This study is intended as a first step towards operability-oriented earthquake forecasting in Japan. Encouragingly, at least one model passed the test in most combinations of the target day and the testing method, although the models could not take account of the megaquake in advance and the catalogue used for forecast generation was incomplete. However, it can also be seen that all models have only limited forecasting power for the period immediately after the quake. Our conclusion does not change when the preliminary JMA catalogue is replaced by the finalized one, implying that the models perform stably over the catalogue replacement and are applicable to operational earthquake forecasting. However, we emphasize the need of further research on model improvement to assure the reliability of forecasts for the days immediately after the main quake. Seismicity is expected to remain high in all parts of Japan over the coming years. Our results present a way to answer the urgent need to promote research on time-dependent earthquake predictability to prepare for subsequent large earthquakes in the near future in Japan.

[1]  David A. Rhoades,et al.  Efficient testing of earthquake forecasting models , 2011 .

[2]  T. Jordan.  Earthquake Predictability, Brick by Brick , 2006 .

[3]  F. Hirose,et al.  Outline of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) —Seismicity: foreshocks, mainshock, aftershocks, and induced activity— , 2011 .

[4]  J. D. Zechar,et al.  Likelihood-Based Tests for Evaluating Space–Rate–Magnitude Earthquake Forecasts , 2009 .

[5]  B. Gutenberg,et al.  Frequency of Earthquakes in California , 1944, Nature.

[6]  Mitsuyuki Hoshiba,et al.  Outline of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) —Earthquake Early Warning and observed seismic intensity— , 2011 .

[7]  A. Ruina.  Slip instability and state variable friction laws , 1983 .

[8]  Jiancang Zhuang,et al.  Next-day earthquake forecasts for the Japan region generated by the ETAS model , 2011 .

[9]  Naoshi Hirata,et al.  Overview of the first earthquake forecast testing experiment in Japan , 2011 .

[10]  S. Wiemer,et al.  A retrospective comparative forecast test on the 1992 Landers sequence , 2011 .

[11]  Warner Marzocchi,et al.  The Assumption of Poisson Seismic-Rate Variability in CSEP/RELM Experiments , 2010 .

[12]  Rodolfo Console,et al.  Short-term and long-term earthquake occurrence models for Italy: ETES, ERS and LTST , 2010 .

[13]  Yosihiko Ogata,et al.  Comprehensive and Topical Evaluations of Earthquake Forecasts in Terms of Number, Time, Space, and Magnitude , 2013 .

[14]  Danijel Schorlemmer,et al.  RELM Testing Center , 2007 .

[15]  S. Wiemer,et al.  Earthquake Likelihood Model Testing , 2007 .

[16]  Philip J. Maechling,et al.  The Collaboratory for the Study of Earthquake Predictability perspective on computational earthquake science , 2010 .

[17]  Matthew C. Gerstenberger,et al.  Real-time forecasts of tomorrow's earthquakes in California , 2005, Nature.

[18]  J. Dieterich.  A constitutive law for rate of earthquake production and its application to earthquake clustering , 1994 .

[19]  Maximilian J. Werner,et al.  Magnitude uncertainties impact seismic rate estimates, forecasts, and predictability experiments , 2007, 0710.4196.

[20]  Y. Kagan,et al.  High-Resolution Long-Term and Short-Term Earthquake Forecasts for California , 2011 .

[21]  Warner Marzocchi,et al.  Real‐time forecasting following a damaging earthquake , 2009 .

[22]  Naoshi Hirata,et al.  CSEP Testing Center and the first results of the earthquake forecast testing experiment in Japan , 2012, Earth, Planets and Space.

[23]  Y. Ogata.  Significant improvements of the space-time ETAS model for forecasting of accurate baseline seismicity , 2011 .

[24]  Y. Ogata.  Seismicity Analysis through Point-process Modeling: A Review , 1999 .

[25]  Danijel Schorlemmer,et al.  First Results of the Regional Earthquake Likelihood Models Experiment , 2010 .