Abstract
AbstractA source model for estimating broad-band ground motions from the 2007 Noto-Hanto earthquake (Mw6.7) is estimated from a comparison of the observed records of the mainshock and synthesized motions based on the characterized asperity model using the empirical Green’s function method. The observed records of aftershocks used as the empirical Green’s functions are carefully selected to have almost the same radiation characteristics and source distance as the asperities of the mainshock. The best-fit source model consists of two asperities of different size. A large one is located just above the hypocenter, with an area of 6.3×6.3 km2and stress drop of about 26 MPa. A smaller one is located north-east of the large one, with an area of 3.6×3.6 km2and stress drop of about 10 MPa. The stress drop of the large one is about twofold higher than the average values of inland crustal earthquakes so far estimated, while that of smaller one is almost average. We found that the remarkable directivity pulses from the source model struck the northern part of the Noto peninsula, causing heavy damage in some towns there.
Highlights
The 2007 Noto-Hanto earthquake (Mw = 6.7) at 9:41:58(JST) on March 25, 2007 occurred west off the Noto peninsula, Japan
The strong ground motions synthesized using the characterized source model are largely influenced by two parameters: asperity area and stress drop on the asperity
The synthesized motions calculated by only Asperity-1 were not able to estimate the second pulse of observed records at ISK003
Summary
(JST) on March 25, 2007 occurred west off the Noto peninsula, Japan. Strong ground motions with a Japan Meteorological Agency (JMA) seismic intensity of 6-upper struck Wajima, Anamizu, and Nanao in the northern part of the Noto peninsula, causing one death, about 300 collapsed houses and about 2000 partially destroyed houses (Fire and Disaster Management Agency, 2007). The earthquake fault was associated with known active faults just off the west shore of the northern part of the Noto peninsula (Katagawa et al, 2005) This fault dips beneath the Noto peninsula, which is consistent to the aftershock distributions and the CMT solutions. This might be one of reasons why the damaged areas extended widely over the northern Noto peninsula, which is located on the hanging wall side of the fault. We attempt to examine whether the above relations are available for modeling the rupture process of the 2007 Noto-Hanto earthquake It is one of the most important issues associated with increasing the reliability of strong motion prediction and risk assessment for future large earthquakes. The analyzed range of frequency was from 0.2 to 10 Hz
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