scholarly journals Weak interplate coupling beneath the subduction zone off Fukushima, NE Japan, inferred from GPS/acoustic seafloor geodetic observation

2008 ◽  
Vol 60 (6) ◽  
pp. e9-e12 ◽  
Author(s):  
Yoshihiro Matsumoto ◽  
Tadashi Ishikawa ◽  
Masayuki Fujita ◽  
Mariko Sato ◽  
Hiroaki Saito ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Geodetic Observation ◽  
Seafloor Geodetic Observation ◽  
Interplate Coupling ◽  
Ne Japan

scholarly journals Heterogeneous interplate coupling along the Nankai Trough, Japan, detected by GPS-acoustic seafloor geodetic observation

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Yusuke Yokota ◽  
Tadashi Ishikawa ◽  
Mariko Sato ◽  
Shun-ichi Watanabe ◽  
Hiroaki Saito ◽  
...  
Keyword(s):  
Nankai Trough ◽  
Geodetic Observation ◽  
Seafloor Geodetic Observation ◽  
Interplate Coupling

Repeating Earthquakes Along the Colombian Subduction Zone

2020 ◽  
Vol 15 (5) ◽  
pp. 645-654
Author(s):  
Juan Carlos Bermúdez-Barrios ◽  
◽  
Hiroyuki Kumagai
Keyword(s):  
Subduction Zone ◽  
Threshold Value ◽  
Waveform Data ◽  
Repeating Earthquakes ◽  
Seismic Waveform ◽  
Interplate Coupling ◽  
Short Period ◽  
Tectonically Active ◽  
Waveform Similarity ◽  
Large Earthquakes

Colombia is tectonically active, and several large earthquakes have ruptured the Colombia-Ecuador subduction zone (CESZ) during the last century. Among them, the Colombia-Ecuador earthquake in 1906 (Mw 8.4) and the Tumaco earthquake in 1979 (Mw 8.3) generated destructive tsunamis. Therefore, it is important to characterize the seismic rupture processes and their relation with interplate coupling along the CESZ. We searched for repeating earthquakes by performing waveform similarity analysis. Cross correlation (CC) values were computed between earthquake pairs with hypocenter differences of less than 50 km that were located in the northern CESZ (1°–4°N) and that occurred from June 1993 to February 2018. We used broadband and short-period seismic waveform data from the Servicio Geológico Colombiano (SGC) seismic network. A CC threshold value of 0.90 was used to identify the waveform similarity and select repeating earthquakes. We found repeating earthquakes distributed near the trench and the coast. Our estimated repeating earthquakes near the trench suggest that the interplate coupling in this region is low. This is in clear constrast to the occurrence of a large slip in the 1906 Colombia-Ecuador earthquake along the trench in the southern part of the CESZ, and suggests that rupture modes are different between the northern and southern parts of CESZ near the trench.

scholarly journals Crustal Deformation Detection Capability Associated With a Fault Slip on the Interplate Boundary in the Gnss-a Seafloor Geodetic Observation Array (SGO-A), Provided By Japan Coast Guard

2021 ◽  
Author(s):  
Yusuke Yokota ◽  
Tadashi Ishikawa ◽  
Sun-ichi Watanabe ◽  
Yuto Nakamura
Keyword(s):  
Standard Deviation ◽  
Crustal Deformation ◽  
Deformation Rate ◽  
Coast Guard ◽  
Detection Sensitivity ◽  
Japan Trench ◽  
Detection Capability ◽  
Geodetic Observation ◽  
Seafloor Geodetic Observation ◽  
Slip Event

Abstract The GNSS-A technique is an observation method that can detect seafloor crustal deformations with centimeter level accuracy. The GNSS-A seafloor geodetic observation array operated by the Japan Coast Guard, called SGO-A, has been constructed near the Japan Islands along the Nankai Trough and the Japan Trench. This observation array has detected several earthquakes’ displacements and episodic slow crustal deformation. To compare the detection results of SGO-A with other observation networks and expand the SGO-A distribution, it is necessary to correctly understand its detection capability. In this paper, the capabilities of current GNSS-A (frequency: f = 4–6 times/year, position accuracy: σ (standard deviation) = 1.5 cm) to detect a crustal deformation rate only, an event only, and crustal deformation rate and event together were arranged by numerical simulations. Results suggested the following features: when it is known that there is no event, the 95% confidence level (CL) for the estimation of crustal deformation rate with 4-year observation is about 0.5–0.8 cm/year; when the deformation rate is known, a signal of about 3.0 cm can be detected by observations of about 4 times before and after the event. When the deformation rate and the event are detected together, to keep the false positive low (about 0.05), the false negative becomes high (about 0.2–0.7 for detecting a signal of 4.5–6.0 cm). The determined rate and event variations are approximately 1.8 cm/year (95%CL) and 1.5 cm (standard deviation), respectively. We also examined the detection capability for higher frequency and accuracy, to examine how the detection capability improves by technological advancements in the future. Additionally, we calculated the spatial range of event detectability using the determined values of detection sensitivity. Each seafloor site can detect a slip event larger than 0.1 m scale within about 50 km radius. A subseafloor slip event smaller than about 1 m at the distance of 100 km or more from the land can often be detected only on the seafloor observation array.

Enhancement of Interplate Coupling after Recent Megathrust Earthquakes

2020 ◽  
Author(s):  
Mohammad Yuzariyadi ◽  
Kosuke Heki
Keyword(s):  
Subduction Zones ◽  
Megathrust Earthquakes ◽  
The North ◽  
Rupture Area ◽  
Interplate Coupling ◽  
Maule Earthquake ◽  
Megathrust Faults ◽  
Adjacent Segments ◽  
Gnss Data ◽  
Ne Japan

<p>Enhanced interplate coupling has been found for segments adjacent along-strike to megathrust faults after the 2003 Tokachi-Oki and the 2011 Tohoku-Oki earthquakes, NE Japan, and was interpreted as acceleration of the subducting Pacific Plate slab. A similar enhanced coupling was also reported for the segments to the north of the rupture area of the 2010 Maule earthquake, central Chile. We utilize available GNSS data to find such enhanced coupling in worldwide subduction zones including NE Japan, central and northern Chile, Sumatra, and Mexico to investigate their common features. Our study revealed that the accelerations of landward movement of 2.1-9.0 mm per year appeared in adjacent segments following the 2014 Iquique (Chile), the 2007 Bengkulu (Sumatra), and the 2012 Oaxaca (Mexico) earthquakes. We also confirmed that the enhanced coupling is associated with the increase of seismicity for all these six cases. We found that the degree of enhancement depends on the length of the slab and the magnitude of the earthquake, which is consistent with the simple 2-dimensional model proposed earlier.</p>

scholarly journals Interplate coupling beneath NE Japan inferred from three-dimensional displacement field

2006 ◽  
Vol 111 (B4) ◽  
Author(s):  
Yoko Suwa ◽  
Satoshi Miura ◽  
Akira Hasegawa ◽  
Toshiya Sato ◽  
Kenji Tachibana
Keyword(s):  
Displacement Field ◽  
Three Dimensional ◽  
Interplate Coupling ◽  
Ne Japan
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