Abstract
In 2004 and 2007, destructive intraplate earthquakes (both MJMA 6.8) occurred in the mid-Niigata region of Japan. High-resolution three-dimensional imaging of the seismic velocities in this area suggests that these events were due to a buried ancient rift and weak zones in and below the seismogenic zone. Using finite element modeling, we simulated the development of fault zones in this region taking into account the buried rift and weak zones in the basement. We set the values of elastic constants and friction coefficients in the sedimentary layer to be smaller than those in the basement, and we set the friction coefficient in the basement to be low in areas of low P-wave velocity. The numerical results show the development of plastic fault zones at concavities along the boundary between the sedimentary layer and basement. Furthermore, fault zones are well developed in those parts of the basement with a small friction coefficient. Fault zones related to the 2004 and 2007 earthquakes are also developed. Our numerical results indicate that buried rift and weak zones in the basement caused the development of the complex fault configuration observed in the mid-Niigata region.
Published Version
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