Open Access

Source processes of the foreshock, mainshock and largest aftershock in the 2003 Miyagi-ken Hokubu, Japan, earthquake sequence

Earth, Planets and Space201456:BF03353392

https://doi.org/10.1186/BF03353392

Received: 28 October 2003

Accepted: 5 February 2004

Published: 29 June 2014

Abstract

The waveform inversions for the 2003 Miyagi-ken Hokubu earthquake sequence were performed using strong-motion records to determine the source processes. We carried out the inversions for the foreshock (M5.6), the mainshock (M6.4) and the largest aftershock (M5.5), respectively. The strong-motion waveforms observed at 10 stations from KiK-net and K-NET within about 70 km epicentral distance were used. The mainshock is composed of two subplanes dipping toward west. The strike direction of the south subplane is NE-SW and that of the north subplane is almost N-S. The fault plane of the foreshock is almost the same as that of the south subplane of the mainshock, but the strike direction of the largest aftershock is NW-SE. The asperities of the three earthquakes are not overlapped strongly each other and it is considered that this earthquake sequence is a result of seismic activity on a reverse fault, which is curved along strike, with time lags. The shallow asperity of the mainshock may result in specific distributions of damage and high accelerations.

Key words

Source process waveform inversion strong motion earthquake sequence