IISEE’s CMTs, Aftershock Distributions, Fault planes, and Rupture models for recent large earthquakes in the world

IISEE’s CMTs, Aftershock Distributions, Fault planes, and Rupture processes for recent large earthquakes in the world [Japanese version]

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[Outline]

The IISEE has started a project to determine the following earthquake information for recent large (Mw≧7.2) earthquakes in the world by the analytical techniques developed by the IISEE staff members and visiting researchers.

n Centroid moment tensor

Centroid moment tensors are determined analyzing long period body wave data recorded at GSN (Global Seismological Network) stations.

u Period: 1994 – October 2010

u Analytical method: Grid search approach by Hara (2004, 2005)

u Principal Investigator: Tatsuhiko Hara (IISEE. E-mail: thara at kenken.go.jp)

n Aftershock distribution and corresponding fault plane

Aftershocks including mainshock and foreshocks are relocated using P-wave arrivals from International Seismological Centre (ISC) CD-ROMs. Then, the corresponding fault plane is determined based on the obtained aftershock distribution (nodal planes are taken from the Global CMT catalog).

u Period: January 1994 – 2007

u Analytical method: The modified joint hypocenter determination method (MJHD. Hurukawa and Imoto, 1992; Hurukawa, 1995; Hurukawa et al., 2008)

u Principal Investigator: Nobuo Hurukawa (IISEE. E-mail: hurukawa at kenken.go.jp)

n Rupture process

Earthquake rupture processes are determined analyzing broadband waveform data recorded at GSN (Global Seismological Network) stations. The above aftershock analyses are referred to set up earthquake fault planes.

u Period: January 1994 – November 2007

u Analytical method: Waveform inversion considering covariance components in inversion analyses of densely sampled observed data by Yagi and Fukahata (2008)

u Principal Investigator: Yuji Yagi (Tsukuba University/ IISEE visiting researcher. E-mail: yagi-y at geol.tsukuba.ac.jp)

● We analyzed large (M≧7) events that occurred between 1976 and 2007 to determine their aftershock distributions and corresponding fault planes to expand the database.

IISEE’s aftershock distributions and corresponding fault planes

● We have developed software to perform strong ground motion simulation for seismic bedrock using stochastic Green’s function method.

● We provide a set of earthquake fault parameters used in tsunami simulations that are presented on the IISEE web site.

● We found azimuthal dependence of high frequency energy radiation for the 2011 Off the Pacific Coast of Tohoku earthquake.