“Œv”—Œค‹†Š

‘ๆ24‰๑“Œv’nkŠwƒZƒ~ƒi[

“๚Žž(Date)
2012”N5ŒŽ11“๚i‹เj/ 11 May 2012 (Friday)
“o˜^•s—vEŽQ‰ม–ณ—ฟ
ŽžŠิ(Time)
14:00-15:00
๊Š
(Location)
“Œv”—Œค‹†Š D312A†Žบ /
Room D312A @ Institute of Statistical Mathematics
u‰‰‘่–ฺ
(Title)
Temporal Changes in Fault Strength and Pore Fluid Pressures Following the 2011 off the Pacific Coast of Tohoku Earthquake
u‰‰Žา
(Speaker)
Ž›์Ž๕Žq
(–ผŒร‰ฎ‘ๅŠw@Šย‹ซŠwŒค‹†‰ศ@•‘ฎ’nk‰ฮŽRŒค‹†ƒZƒ“ƒ^[)
ŠT—v
(Abstract)

Extensive aftershocks and triggered seismic events are ubiquitous following large earthquakes, but the controlling mechanisms are not yet understood. Focal mechanisms of these events can provide insight into physical triggering mechanisms because they reflect friction coefficient and pore fluid pressure on the fault as well as the tectonic stress pattern. In the present study we investigate physical processes triggering seismic events in inland region of the northeast Japan following the 2011 off the Pacific Coast of Tohoku earthquake (Mw = 9. 0) by examining focal mechanisms to the tectonic stress pattern and changes in the Coulomb failure function (DCFF). The local excitation of seismicity rate in the regions with negative DCFF indicates that these aftershocks would have been triggered by decrease of fault strength due to the increase of pore fluid pressures. We show a plausible explanation that seismic events on unfavourably oriented pre-existing faults relative to the tectonic stress pattern, or focal mechanisms inconsistent with the tectonic stress pattern, would be evidence for drastic decrease of fault strength due to increase of pore fluid pressures.

ฃ ‚ฑ‚ฬƒy[ƒW‚ฬƒgƒbƒv‚ึ