Joint inversion of strong motion and geodetic data for the source process of the 2003 Tokachi-oki, Hokkaido, earthquake

• Published in: Earth, planets, and space planets, and space, 2004-01, Vol.56 (3), p.329-334
• Main Authors: Koketsu, Kazuki, Hikima, Kazuhito, Miyazaki, Shin’ichi, Ide, Satoshi
• Format: Article
• Language: English
• Subjects: Asperity; Datasets; Earthquakes; Inversions; S waves; Seismic activity; Slip; Subduction (geology); Wave velocity
• ISSN: 1880-5981; 1343-8832; 1880-5981
• DOI: 10.1186/BF03353060

The strong motion and geodetic data were individually inverted for the source process of the 2003 Tokachi-oki, Hokkaido, earthquake with a hypocenter 25 km deep and a fault plane above the subducting Pacific slab. Both the results show a simple slip distribution with a single major asperity, but the strong motion inversion may include a trade-off between slip location and rupture time and the geodetic inversion does not have sufficient resolution for far slips. We then carred out a joint inversion of the two datasets in order to overcome these weaknesses of the single dataset inversions. The resultant slip distribution still retains the simple pattern and has a seismic moment of 2.2 × 1021 N·m (Mw 8.2). The asperity, with a peak slip of 7.1 m, is located in the center of the fault plane 50 km away from the hypocenter in the down-dip direction. The slip rate functions on subfaults around the hypocenter and asperity indicate that the rupture propagated with a supershear speed on the upper part of the fault plane and slowed down to 100–90% of the S-wave velocity on the middle and lower parts. These simple slip patterns and near-supershear rupture may imply the maturity of the Hokkaido subduction zone around the source region.