反射法地震探査・余震観測・地殻変動から見た2007年能登半島地震の特徴について

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The geophysical and geological characters of the source fault of the Noto Hanto earthquake (MJMA 6.9) were synthesized. Based on the seismic profiles acquired by two-ship seismic reflection profiling and aftershock distribution determined by densely deployed seismic stations, we constructed the 3D geometry of the source fault, trending ENE to NE and dipping 60 degrees south. Around the focal area, detailed topography and bathymetry had been measured by laser scanning and echo sounding before the earthquake. Unique data on onshore-offshore co-seismic crustal movements were obtained from careful comparisons with new data acquired after the earthquake. Using the 3D geometry of the source fault and the co-seismic crustal movements, slip distribution on the fault surface was estimated by 3D dislocation inversion. The obtained pattern of slip distribution shows that the largest slip area is on a relatively shallow part of the fault surface, which coincides with the location of a known active fault. The seismic reflection profiles and surface geo-logy suggest that the source fault was formed as a normal fault during the stage of backarc rifting in Oligocene to early Miocene. The 2007 Noto Hanto earthquake was generated by an oblique slip on the Miocene normal fault. The landward extension of the source fault, which bounds the Miocene half-graben, is traceable by seismic reflection profiling and gravity anomaly. The eastern end of the source fault is bounded by a syn-rift transfer fault, suggesting strong control of the crustal structure on the behavior of the earthquake source fault.
東京大学の論文
2008-03-26

反射法地震探査・余震観測・地殻変動から見た2007年能登半島地震の特徴について

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