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Seismological investigation of deep structure of active faults using scattered waves and trapped waves
Published in H. Ogasawara, T. Yanagidani, M. Ando, Seismogenic Process Monitoring, 2017
The analysis methods using scattered waves and fault-zone trapped waves are discussed. The scattering tomography is an effective approach to survey the regional, 3-D heterogeneous structure, and detailed scatterer distribution was estimated along the San Andreas fault system by using a dense station and event data. Further systematic analyses using the database of seismographic network over Japan will bring the fundamental understanding of scattering properties, i.e. heterogeneous structure along the active faults. The method using fault-zone trapped waves is found to be another effective way to reveal a detailed structure of active faults, i.e. fault-zone inner properties such as width, velocity and attenuation, and also the fault plane geometry. Fault-zone trapped waves have been extensively observed along the surface ruptures of recent large earthquakes in the US, Japan, and Turkey. These studies will lead to a comprehensive understanding of the fault zone properties (damaged zone) related to the earthquake rupture process. Temporal and spatial (along-strike) change of the fault zone structure will also be important study subjects for elucidating earthquake cycles and fault-plane heterogeneities, respectively.
Prediction of near fault ground motion by dynamic rupture simulation
Published in Ömer Aydan, Takashi Ito, Takafumi Seiki, Katsumi Kamemura, Naoki Iwata, 2019 Rock Dynamics Summit, 2019
M. Yamada, R. Imai, K. Takamuku, H. Fujiwara
Tsuda (2016) tried to reproduce the rupture process of mega-thrust earthquakes such as the 2011 off the Pacific coast of Tohoku Earthquake. Kase (2016) tried to explain the source process of the intersegmental rupture propagation for the 2014 northern Nagano earthquake. Kase et al. (2002) simulated the earthquake rupture process on the Uemachi fault system. Irie (2014) explored to be clear for the source properties of large inland strike-slip faults for strong motion prediction based on dynamic rupture simulation. However, in these simulations, the initial rupture area that was given smaller static friction coefficient and the rupture stop area in which rupture was not permitted were indispensable.
Dynamic responses and stability of historical structures and monuments
Published in Ömer Aydan, Rock Dynamics, 2017
The Great Hanshin earthquake or Kobe earthquake, occurred on Tuesday, January 17, 1995, at 05:46 JST (January 16 at 20:46 UTC) in the southern part of Hyōgo Prefecture, Japan. It measured 6.8 on the moment magnitude scale and Mj7.3 (adjusted from 7.2) on JMA magnitude scale. The total earthquake rupture time was 20 seconds and the hypocenter was 16 km deep. Besides tremendous damage and heavy casualties many masonry type structures were affected by this earthquake. Figure 9.14 shows the dislocation of granitic blocks of a temple in Kobe City.
Mechanism for seismic supershear dynamic rupture based on in-situ stress: a case study of the Palu earthquake in 2018
Published in Geomatics, Natural Hazards and Risk, 2022
Kanghua Zhang, Yishuo Zhou, Yimin Liu, Pu Wang
Driven by these results, we first used a method of constraining the in-situ stress using a lateral pressure coefficient polygon and a focal mechanism solution (FMS; Wang et al. 2019). To improve the accuracy of the constraint results, a normal distribution analysis was conducted on the shape ratio of the FMS. Second, the three-sigma rule is used to further constrain the deep lateral pressure coefficient in the Palu area, and the deep stress state of the fault plane is calculated according to the occurrence of the fault. Finally, we used the open-source software, Pylith (Aagaard et al. 2013) to establish a 2 D Palu fault model (mainly considering the strike feature) and simulate the earthquake rupture process. The results show that stable supershear rupture occurred approximately 7 s after the onset of rupture when the rupture front reached Palu Bay, by considering both the in-situ stress field and fault structure. Simultaneously, there is an apparent Mach cone phenomenon causing a much greater surface displacement than in other regions, which shows a high degree of similarity to the SAR analysis and geodetic data. The numerical simulation of earthquake rupture, based on the in-situ stress and fault structure, also aids in predicting the level of seismic damage and provides implications for the mitigation of seismic risks.
A new tsunami hazard assessment for eastern Makran subduction zone by considering splay faults and applying stochastic modeling
Published in Coastal Engineering Journal, 2023
Payam Momeni, Katsuichiro Goda, Mohammad Mokhtari, Mohammad Heidarzadeh
Since splay faults are relatively weak zones, they can be chosen as pathways for rupture propagation of earthquakes from the main subduction interface. Although it is possible that the interseismic elastic strains of the subduction zones could be fully released by the splay fault ruptures, it is more likely that the earthquake rupture initiates on the main subduction zone interface followed by slip partitioning between the subduction zone plate boundary and splay faults (Park et al. 2002). Kame and Yamashita (1999) showed that due to the stress field of the accretionary prism, earthquake rupture that propagates up-dip from the nucleation of great interplate earthquakes in the subduction zones tends to branch into the accretionary prism and partition between steeply-dipping thrust splay faults and the main subduction plate interface. This partitioning is more likely to occur in the parts of the accretionary prism where the horizontal compression stress due to the subduction is the major component of the stress field. These parts include the early-stage accretionary prism near the trench line and the landward side of topographic highs which do not experience significant overburden pressure compared to their horizontal compression stress (Kame and Yamashita 1999). Although it is unknown if the splay faults can rupture occasionally by themselves, a recent study on the 2019 Mw 7.2 Molucca Sea earthquake showed that the splay faults in that region can generate tsunamis (Heidarzadeh et al. 2021; Sykes and Menke 2006). Due to their steep dip angles, splay ruptures result in significant vertical deformation of the seabed and can generate large tsunamis. The rupture of splay faults usually affects near-field local areas due to their smaller sizes compared to the plate boundary faults (Heidarzadeh, Pirooz, and Zaker 2009). In the MSZ, several splay faults have been located both in the eastern and western parts of the subduction zone (Grando and McClay 2007; Mokhtari, Fard, and Hessami 2008; Mokhtari 2015; Smith et al. 2012). Due to the presence of splay faults in the MSZ and considering significant tsunamis that splay faults have caused in other subduction zones, the effects of splay fault ruptures on tsunami hazards need to be studied for the Makran region.