Mechanisms of large earthquakes along the eastern margin of the Japan sea

• Main Authors: Yoshio Fukao, Muneyoshi Furumoto
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1975
• Subjects: Sakhalin
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.456.8841; http://www.openseismo.org/contributors/Lee/MoWorking_Backups/Mo2012_0424backup/MoWorking_OLD2/Paper_Pending/Fukao-Furumoto_Tectonophys1974_v26p247.pdf

Fukao, Y. and Furumoto, M., 1975. Mechanism of large earthquakes along the eastern margin of the Japan Sea. Tectonophysics, 25: 247-266 The source mechanisms of large earthquakes occurring along the eastern margin of the Japan Sea are investigated. The earthquakes studied are those off Oga (May 7, 1964), Sakhalin (Sep. 5, 1971) and Shakotan (Aug. 1, 1940) and, though supplementary, the Niigata (Jun. 16, 1964) earthquake. The focal mechanisms of these four earthquakes are predominantly dip-slip reverse faulting on a plane dipping relatively steeply. The strikes of the fault planes are parallel to the general trend of the eastern margin of the Japan Sea. The parameters for the dislocation are determined on the basis of the long-period surface waves and the tsunami heights at the coasts. The stress drop of 126 bars for the Niigata earthquake is significantly large compared to those for the other three shocks. The smallest is the stress drop of 17 bars for the earthquake off Shakotan. This earthquake was found to be especially interesting in two respects. First, the relative excitation of the short- and long-period seismic waves and the tsunami suggests that the dislocation of 1.1 m took place with an abnormally lon exceptionally large area of 50 X 170 km P duration. Second, the fault plane involves an. This fault plane cuts through the entire thick-ness of the lid on the low-velocity zone developing beneath the Japan Sea. The fault plane may manifest a pre-existing fractured zone by which the Japan Sea lithosphere is separated from the northern Japan arc, as far as the west of Hokkaido is concerned.