Hypocenters in the Nankai Trough Determined by Using Data from Both Ocean‐Bottom and Land Seismic Networks and a 3D Velocity Structure Model: Implications for Seismotectonic Activity

2015 ◽  
Vol 105 (3) ◽  
pp. 1594-1605 ◽  
Author(s):  
Masaru Nakano ◽  
Takeshi Nakamura ◽  
Yoshiyuki Kaneda
Keyword(s):  
Velocity Structure ◽  
Nankai Trough ◽  
Ocean Bottom ◽  
Structure Model ◽  
Using Data ◽  
Seismotectonic Activity ◽  
Seismic Networks

scholarly journals Centroid moment tensor inversions of offshore earthquakes using a three-dimensional velocity structure model: slip distributions on the plate boundary along the Nankai Trough

2020 ◽  
Vol 222 (2) ◽  
pp. 1109-1125 ◽  
Author(s):  
Shunsuke Takemura ◽  
Ryo Okuwaki ◽  
Tatsuya Kubota ◽  
Katsuhiko Shiomi ◽  
Takeshi Kimura ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
Velocity Structure ◽  
Nankai Trough ◽  
Moment Tensor ◽  
Plate Boundary ◽  
Seismic Wave Propagation ◽  
Structure Model ◽  
Centroid Moment Tensor ◽  
Heterogeneous Distribution

SUMMARY Due to complex 3-D heterogeneous structures, conventional 1-D analysis techniques using onshore seismograms can yield incorrect estimation of earthquake source parameters, especially dip angles and centroid depths of offshore earthquakes. Combining long-term onshore seismic observations and numerical simulations of seismic wave propagation in a 3-D model, we conducted centroid moment tensor (CMT) inversions of earthquakes along the Nankai Trough between April 2004 and August 2019 to evaluate decade-scale seismicity. Green's functions for CMT inversions of earthquakes with moment magnitudes of 4.3–6.5 were evaluated using finite-difference method simulations of seismic wave propagation in the regional 3-D velocity structure model. Significant differences of focal mechanisms and centroid depths between previous 1-D and our 3-D catalogues were found in the solutions of offshore earthquakes. By introducing the 3-D structures of the low-velocity accretionary prism and the Philippine Sea Plate, dip angles and centroid depths for offshore earthquakes were well-constrained. Teleseismic CMT also provides robust solutions, but our regional 3-D CMT could provide better constraints of dip angles. Our 3-D CMT catalogue and published slow earthquake catalogues depicted spatial distributions of slip behaviours on the plate boundary along the Nankai Trough. The regular and slow interplate earthquakes were separately distributed, with these distributions reflecting the heterogeneous distribution of effective strengths along the Nankai Trough plate boundary. By comparing the spatial distribution of seismic slip on the plate boundary with the slip-deficit rate distribution, regions with strong coupling were clearly identified.

Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami

2021 ◽  
Author(s):  
Jui-Chun Freya Chen ◽  
Wu-Cheng Chi ◽  
Chu-Fang Yang
Keyword(s):  
Deep Ocean ◽  
Propagation Model ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Tsunami Propagation ◽  
Ground Tilt ◽  
Tsunami Waves ◽  
The Pacific ◽  
Seismic Networks ◽  
Back Azimuth

Abstract Developing new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

Ocean-Bottom Strong-Motion Observations in the Nankai Trough by the DONET Real-Time Monitoring System

2018 ◽  
Vol 52 (3) ◽  
pp. 100-108 ◽  
Author(s):  
Takeshi Nakamura ◽  
Narumi Takahashi ◽  
Kensuke Suzuki
Keyword(s):  
Real Time ◽  
Nankai Trough ◽  
Strong Motion ◽  
Deep Ocean ◽  
Disaster Mitigation ◽  
Ocean Bottom ◽  
Source Modeling ◽  
Origin Time ◽  
Subduction Earthquakes ◽  
Sediment Layers

AbstractThe deployment of real-time permanent ocean-bottom seismic and tsunami observatories is significant for disaster mitigation and prevention during the occurrence of large subduction earthquakes near trough areas. On April 1, 2016, a moderate-sized suboceanic earthquake occurred beneath Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) stations that were recently deployed in deep ocean-bottom areas near the Nankai Trough in southwest Japan. P-waves arrived at the ocean-bottom station within 4 s of the origin time, which was 6 and 13 s earlier than the arrival of P- and S-waves at a land station in the coastal area, respectively; this implies earlier detection of strong motion than at land stations. However, the waveforms are amplified by sediment layers and even contaminated with acceleration offsets at some stations, which would lead to overestimations during source investigations. Such amplification and offset did not occur at a borehole station connected to DONET. The amplifications caused by the sediment layers and the offset were found to have a considerable spatial variation, not only between the DONET stations and land and borehole stations but also among the DONET stations, implying that the amplitude evaluation could be unstable. Therefore, procedures for correcting or suppressing the amplification and offset problem are required for conducting waveform analyses, such as magnitude estimations and source modeling, during large subduction earthquakes.

scholarly journals Western Nankai Trough seismogenic zone: Results from a wide-angle ocean bottom seismic survey

2000 ◽  
Vol 105 (B3) ◽  
pp. 5887-5905 ◽  
Author(s):  
Shuichi Kodaira ◽  
Narumi Takahashi ◽  
Jin-Oh Park ◽  
Kimihiro Mochizuki ◽  
Masanao Shinohara ◽  
...  
Keyword(s):  
Nankai Trough ◽  
Seismic Survey ◽  
Seismogenic Zone ◽  
Ocean Bottom ◽  
Wide Angle

Three-dimensional crustal velocity structure model of the middle-eastern north China Craton (HBCrust1.0)

2016 ◽  
Vol 59 (7) ◽  
pp. 1477-1488 ◽  
Author(s):  
YongHong Duan ◽  
FuYun Wang ◽  
XianKang Zhang ◽  
JiYan Lin ◽  
Zhi Liu ◽  
...  
Keyword(s):  
North China Craton ◽  
North China ◽  
Velocity Structure ◽  
Middle Eastern ◽  
Three Dimensional ◽  
Structure Model ◽  
Crustal Velocity ◽  
Crustal Velocity Structure
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