INTERPRETATION OF LARGE-AMPLITUDE VELOCITY PULSES DURING THE 2016 KUMAMOTO EARTHQUAKE AND THE EFFECTS OF THE SHALLOW AND DEEP PARTS OF THE FAULT RUPTURES ON THE NEAR-FAULT GROUND MOTIONS

2020 ◽  
Vol 85 (773) ◽  
pp. 879-889
Author(s):  
Toshimichi KIDOH ◽  
Masayuki NAGANO
Keyword(s):  
Large Amplitude ◽  
Ground Motions ◽  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
Near Fault ◽  
The 2016 Kumamoto Earthquake

Dynamic Rupture Study of Near-Field Velocity Pulses during the 2016 Kumamoto Earthquake, Japan

2021 ◽  
Author(s):  
Kenichi Tsuda
Keyword(s):  
Ground Motions ◽  
2016 Kumamoto Earthquake ◽  
Dynamic Rupture ◽  
Velocity Pulse ◽  
Geometrical Properties ◽  
Kumamoto Earthquake ◽  
Near Fault ◽  
The 2016 Kumamoto Earthquake ◽  
Simulated Ground Motions ◽  
Shallow Part

ABSTRACT Simulating the ground motions of future earthquakes requires a proper understanding and modeling of source, path, and site effects. Ground motions recorded during recent earthquakes very close to their ruptured faults provide new evidence of the importance of source effects and suggest that physics-based rupture modeling is critical to account for them. Here, we develop dynamic rupture models to simulate the near-fault ground motions generated by the 2016 Kumamoto, Japan, earthquake (Mw 7.0) at Nishihara village, which feature a large-amplitude velocity pulse. Comparison of mainshock and foreshock waveforms suggests that the source of the velocity pulse is on the Futagawa fault segment located very close to the site. Our dynamic models use the spectral element method and are built upon a previous kinematic description of the event via a so-called “characterized source model,” with three strong-motion generation areas (SMGAs) on the assumed fault plane. We first develop a reference model that reproduces the main features of the rupture process in agreement with previous results of kinematic source inversion. We then examine the sensitivity of the simulated near-fault ground motions to the frictional parameters (critical slip-weakening distance and stress drop) in the shallow part of the fault and to the geometrical properties of the shallow SMGA. Even assuming drastically different frictional properties in the shallow part of the fault, the amplitude of the simulated ground motions was affected little. On the other hand, changes of geometrical properties of the shallow SMGA generated large differences in simulated ground motions. The results indicate that geometrical features of the shallow SMGA played a more important role in generating near-fault ground motions with velocity pulses as observed at Nishihara village during the 2016 Kumamoto earthquake.

scholarly journals Simulation of building damage distribution in downtown Mashiki, Kumamoto, Japan caused by the 2016 Kumamoto earthquake based on site-specific ground motions and nonlinear structural analyses

2021 ◽  
Author(s):  
Jikai Sun ◽  
Fumiaki Nagashima ◽  
Hiroshi Kawase ◽  
Shinichi Matsushima ◽  
Baoyintu
Keyword(s):  
Ground Motions ◽  
Target Area ◽  
2016 Kumamoto Earthquake ◽  
Ground Acceleration ◽  
Site Specific ◽  
Construction Period ◽  
Kumamoto Earthquake ◽  
Velocity Models ◽  
The 2016 Kumamoto Earthquake ◽  
Wooden Structures

AbstractMost of the buildings damaged by the mainshock of the 2016 Kumamoto earthquake were concentrated in downtown Mashiki in Kumamoto Prefecture, Japan. We obtained 1D subsurface velocity structures at 535 grid points covering this area based on 57 identified velocity models, used the linear and equivalent linear analyses to obtain site-specific ground motions, and generated detailed distribution maps of the peak ground acceleration and velocity in Mashiki. We determined the construction period of every individual building in the target area corresponding to updates to the Japanese building codes. Finally, we estimated the damage probability by the nonlinear response model of wooden structures with different ages. The distribution map of the estimated damage probabilities was similar to the map of the damage ratios from a field survey, and moderate damage was estimated in the northwest where no damage survey was conducted. We found that both the detailed site amplification and the construction period of wooden houses are important factors for evaluating the seismic risk of wooden structures.

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