کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6430665 | 1634808 | 2012 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Megaquake cycle at the Tohoku subduction zone with thermal fluid pressurization near the surface Megaquake cycle at the Tohoku subduction zone with thermal fluid pressurization near the surface](/preview/png/6430665.png)
For the 2011 Tohoku earthquake, we propose a mechanical model to explain rare giant (M9-class) and frequent large (M7-class) earthquakes on a thrust fault in the subduction zone. Observations implied, in the M9 Tohoku earthquake, that extremely large slip on the order of tens of meters occurs in a shallower part to release a slip deficit, as well as substantial slip about ten meters or so in a deeper part including the source area of the M7-class earthquakes. Here, we present a model in which the extremely large slip is caused by hydrothermal weakening (dynamic thermal pressurization of pore fluid) on the fault plane, not by contrast of frictional properties in terms of rate- and state-dependent friction. The model explains that the Tohoku earthquake followed a M7-class earthquake in two days, but M7-class earthquakes are not always followed by a giant earthquake. In a giant event, large coseismic slip can occur over an area where quasistatic slip, namely, afterslip of M7-class earthquakes or spontaneous slow slip events, takes place. Slight differences of stress state in the shallow part can result in drastically different coseismic slips. We further perform numerical experiments varying hydraulic parameters and the length of effective hydrothermal weakening area. The experiments imply that observations for monitoring the effective hydrothermal weakening area need spatial resolution on the order of 10Â km or finer.
⺠A long-term mechanical model for the 2011 Tohoku earthquake. ⺠Local large stress drop due to fluid pressurization by shear heating. ⺠Huge seismic slip at not a strong region. ⺠Nonlinear effects of dynamically weakening reflecting absolute stress level.
Journal: Earth and Planetary Science Letters - Volumes 325â326, 1 April 2012, Pages 21-26