Options
Zhuang, J.
Loading...
3 results
Now showing 1 - 3 of 3
- PublicationRestrictedStatistics between mainshocks and foreshocks in Italy and Southern California(2011)
; ; ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zhuang, J.; Institute of Statistical Mathematics, Tokyo, Japan; The most used and accepted models for daily forecasts are based on short‐term space and time earthquake clustering for occurrence rates and on the Gutenberg‐ Richter law for the frequency‐magnitude. These models have been demonstrated to produce reliable prospective space‐time‐magnitude forecasts during an aftershock sequence, but their skill in forecasting mainshocks is still under discussion. This paper studies the foreshock statistics of the Italian and Californian seismicity in two ways: i) we compare the foreshock activity observed in real seismic catalogs and in synthetic catalogs derived from a pure Epidemic‐Type Aftershock Sequence (ETAS) model; ii) we analyze the triggering capability of earthquakes using different ETAS parameterizations, in order to check whether large events are triggered in the same way as regular earthquakes. The results indicate that the foreshock activity observed in the real catalogs is compatible with what is expected by the ETAS model. Moreover, we find that the empirical foreshock rates have an intrinsic variability due to limited sampling that may explain most of the differences found so far in different seismic catalogs.132 26 - PublicationRestrictedPredictability study on the aftershock sequence following the 2011 Tohoku-Oki, Japan, earthquake: first results(2012-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ;Nanjo, K. Z.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Tsuruoka, H.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Yokoi, S.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Ogata, Y.; Institute of Statistical Mathematics, Tokyo, Japan ;Falcone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Hirata, N.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Ishigaki, Y.; Japan Meteorological Agency, Tokyo, Japan ;Jordan, T. H.; Southern California Earthquake Center, University of Southern California, Los Angeles, CA, USA ;Kasahara, K.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Obara, K.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan. ;Schorlemmer, D.; Southern California Earthquake Center, University of Southern California, Los Angeles, CA, USA ;Shiomi, K.; National Research Institute for Earth Science and Disaster Prevention, Ibaraki, Japan ;Zhuang, J.; Institute of Statistical Mathematics, Tokyo, Japan; ; ; ; ; ; ; ; ; ; ; ; 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 JMAcatalogue 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.307 32 - PublicationOpen AccessShort-term earthquake forecasting experiment before and during the L’Aquila (central Italy) seismic sequence of April 2009(2014-11-01)
; ; ; ; ;Murru, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zhuang, J.; Institute of Statistical Mathematics ;Rodolfo, C.; Centro di Geomorfologia Integrata per l'Area Mediterranea ;Giuseppe, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; In this paper, we compare the forecasting performance of several statistical models, which are used to describe the occurrence process of earthquakes in forecasting the short-term earthquake probabilities during the L’Aquila earthquake sequence in central Italy in 2009. These models include the Proximity to Past Earthquakes (PPE) model and two versions of the Epidemic Type Aftershock Sequence (ETAS) model. We used the information gains corresponding to the Poisson and binomial scores to evaluate the performance of these models. It is shown that both ETAS models work better than the PPE model. However, in comparing the two types of ETAS models, the one with the same fixed exponent coefficient (alpha) = 2.3 for both the productivity function and the scaling factor in the spatial response function (ETAS I), performs better in forecasting the active aftershock sequence than the model with different exponent coefficients (ETAS II), when the Poisson score is adopted. ETAS II performs better when a lower magnitude threshold of 2.0 and the binomial score are used. The reason is found to be that the catalog does not have an event of similar magnitude to the L’Aquila mainshock (Mw 6.3) in the training period (April 16, 2005 to March 15, 2009), and the (alpha)-value is underestimated, thus the forecast seismicity is underestimated when the productivity function is extrapolated to high magnitudes. We also investigate the effect of the inclusion of small events in forecasting larger events. These results suggest that the training catalog used for estimating the model parameters should include earthquakes of magnitudes similar to the mainshock when forecasting seismicity during an aftershock sequence.434 271