Abstract
Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.
Highlights
Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures
Previous studies on the rupture process[14,15,16,17,18,19,20,21] and coseismic slip distribution[22,23,24,25] of the M9.0 2011 Tohoku Earthquake occurred on 11 March 2011 have consistently revealed that substantial amount of coseismic slip of B10 m occurred on the deep potion of the plate interface as well as the extremely large (430 m) coseismic slip on the shallow fault, the models show significant diversities in detailed slip pattern reflecting the differences in the data, analysis procedure and assumed structure[14,15,16,17,18,19,20,21,22,23,24,25]
The results reveal that the area in which large postseismic slip occurred on the plate interface can be generally divided into three subareas: (1) the intermediate to deep portion in the latitude range of 38.5–40.2°N; (2) the intermediate portion in the latitude range of 37.5–38.1°N; and (3) the shallow portion in the latitude range of 35.0–36.5°N
Summary
Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures Such spatial separation is expected from the difference in frictional and material properties in and around the faults. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which agreed with the activities of interplate and repeating earthquakes These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes. We investigated the spatial distribution of the postseismic slip on the plate interface This was based on both terrestrial GPS data and seafloor geodetic observations composed of GPS/Acoustic (GPSA) survey results and ocean-bottom pressure (OBP) gauges records. The result suggests that the conventional frictional property model based on the rate- and state-dependent friction law is valid for the source region of the gigantic earthquake
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