The 1995 Kobe earthquake: Seismic image of the source zone and its implications for the rupture nucleation

Mesoscopic structure of the Punchbowl Fault, Southern California and the geologic and geophysical structure of active strike-slip faults

“…Our data do not help explain what produces the very wide (2±3 km) LVZ often described in seismic pro®les (Feng and McEvilly, 1983;Roure et al, 1989;Eberhart-Phillips et al, 1995;Eberhart-Phillips and Reyners, 1997;Stern and McBride, 1998;Zhao and Negishi, 1998). One possibility is that such zones consist of numerous principal slip surfaces with overlapping damaged zones.…”

Crack density and saturation rate in the 1995 Kobe Earthquake Region

“…There is no volcanic or geothermal anomaly in the Kobe region, and hence changes in Vp, Vs and u are attributed mainly to cracks and fluids in the crust by taking into account many pieces of evidence [Zhao and Negishi, 1998], though a fraction of the velocity changes may be caused by lithologic variations. Following OB74 and Kuwahara e!…”

“…A highresolution tomographic study revealed that the Kobe mainshock hypocenter is located in a distinctive zone characterized by low P and $ wave velocities and a high Poisson's ratio [Zhao et al, 1996;Zhao and Negishi, 1998]. The anomalous zone exists in the depth range of 16 to 21 km and extends 15 to 20 km laterally, and is interpreted as a fluid-filled, fractured rock matrix that contributed to the initiation of the Kobe earthquake [Zhao and Negishi, 1998]. Other studies of the Kobe Copyright 1999 by the American Geophysical Union.…”

Hypocenter distribution and heterogeneous seismic velocity structure in and around the focal area of the 2008 Iwate-Miyagi Nairiku Earthquake, NE Japan—Possible seismological evidence for a fluid driven compressional inversion earthquake

“…Such low-velocity regions beneath the focal area of inland earthquakes in Japan can be commonly seen and interpreted as the region with overpressurized uid, which promote the occurrence of inland earthquake; for example, the 1995 southern Hyogo (M 7.2) (Zhao et al, 1996;Zhao and Negishi, 1998), the 2000 western Tottori (M 7.3) (Zhao et al, 2004), the 1962 northern Miyagi (M 6.2) (Nakajima and Hasegawa, 2003), the 2004 Niigata-Chuetsu (M 6.8) Wang and Zhao, 2006) and the 2007 Noto-Hanto (M 7.3) and Niigata-Chuetsu-Oki (M 6.8) (Nakajima and Hasegawa, 2008). This suggests that crustal uid was involved also in the occurrence of the 2008 earthquake.…”