eprintid: 1405 rev_number: 12 eprint_status: archive userid: 2 dir: disk0/00/00/14/05 datestamp: 2015-02-24 11:37:45 lastmod: 2017-02-08 12:21:38 status_changed: 2015-04-27 12:10:50 type: article metadata_visibility: show creators_name: Ma, Kuo-Fong creators_name: Chan, Chung-Han creators_name: Stein, Ross corp_creators: Institute of Geophysics, National Central University, Chung-Li, Taiwan corp_creators: Institute of Geophysics, National Central University, Chung-Li, Taiwan corp_creators: U.S. Geological Survey, Menlo Park, California, USA title: Response of seismicity to Coulomb stress triggers and shadows of the 1999Mw= 7.6 Chi-Chi, Taiwan, earthquake ispublished: pub subjects: SS divisions: EPOS-P full_text_status: none abstract: The correlation between static Coulomb stress increases and aftershocks has thus far provided the strongest evidence that stress changes promote seismicity, a correlation that the Chi-Chi earthquake well exhibits. Several studies have deepened the argument by resolving stress changes on aftershock focal mechanisms, which removes the assumption that the aftershocks are optimally oriented for failure. Here one compares the percentage of planes on which failure is promoted after the main shock relative to the percentage beforehand. For Chi-Chi we find a 28% increase for thrust and an 18% increase for strike-slip mechanisms, commensurate with increases reported for other large main shocks. However, perhaps the chief criticism of static stress triggering is the difficulty in observing predicted seismicity rate decreases in the stress shadows, or sites of Coulomb stress decrease. Detection of sustained drops in seismicity rate demands a long catalog with a low magnitude of completeness and a high seismicity rate, conditions that are met at Chi-Chi. We find four lobes with statistically significant seismicity rate declines of 40–90% for 50 months, and they coincide with the stress shadows calculated for strike-slip faults, the dominant faulting mechanism. The rate drops are evident in uniform cell calculations, 100-month time series, and by visual inspection of the M ≥ 3 seismicity. An additional reason why detection of such declines has proven so rare emerges from this study: there is a widespread increase in seismicity rate during the first 3 months after Chi-Chi, and perhaps many other main shocks, that might be associated with a different mechanism. date: 2005-05-28 date_type: published publication: Journal of Geophysical Research volume: 110 number: B5 publisher: American Geophysical Union pagerange: 1-16 id_number: doi:10.1029/2004JB003389 refereed: TRUE issn: 0148-0227 official_url: http://dx.doi.org/10.1029/2004JB003389 access_IS-EPOS: limited owner: Publisher citation: Ma, Kuo-Fong and Chan, Chung-Han and Stein, Ross (2005) Response of seismicity to Coulomb stress triggers and shadows of the 1999Mw= 7.6 Chi-Chi, Taiwan, earthquake. Journal of Geophysical Research, 110 (B5). pp. 1-16. DOI: https://doi.org/10.1029/2004JB003389