open access

https://doi.org/10.14943/gbhu.69.233

https://hdl.handle.net/2115/21512

Crust Structure at Teshikaga region, Eastern Hokkaido, demonstrated by wide-band magnetotelluric and gravity surveys

日本語

2006-03-15

北海道大学大学院理学研究科地球惑星科学専攻（地球物理学）

Geophysical bulletin of Hokkaido University

69

233-255

Wide-band magnetotelliric and gravity surveys were conducted at the Teshikaga area, located in eastern Hokkaido, Japan, where intra-plate earthquakes had teken place. We inferred shallower (<2-Km depth) crustal density structur using the gravity and borehole data, and then compared it with resistivity structure revealed by two-dimensional MT inversions. The results show that the density and resistivity structures are closely correlated with each other. The resistivity profiles and Bouguer anomaly map indicate that the high density and high resistivity zone, which presumably represents Miocene volcanic and sedimentary rocks is apparently cut by a major dextral strike slip fault. Location and strike of the apparent dextral strike slip fault closely match those of the inferred earthquake fault formed by the 1938's earthquake estimated from surface displacement. However, the dextral strike slip movement is not the result of recent crustal movement, because sinistral movement has been documented for the earthquake faults. Preexisting dextral strike slip fault was presumably reactivated to cause present-day earthquakes.

紀要論文

Version of Record

0439-3503

AN0008976X