Stress, strain rate and anisotropy in Kyushu, Japan

Savage, Martha K.; Aoki, Yosuke; Unglert, K.; Ohkura, Takahiro; Umakoshi, Keisuke; Shimizu, Hiroshi; Iguchi, Masato; Tameguri, Takeshi; Ohminato, Takao; Mori, James

doi:10.1016/j.epsl.2016.01.005

Cited by 54 publications

(54 citation statements)

References 44 publications

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“…Often measurements at a single station may be consistent for the same earthquake location but vary for different earthquake locations (Johnson et al, ; Zhang et al, ). Yet when splitting measurements are averaged regionally, the measurements should align with the maximum horizontal stress (Savage et al, ), although sometimes they are more consistent with regional structures or with faulting (Balfour et al, ; Zinke & Zoback, ).…”

Section: Methodsmentioning

confidence: 99%

Stress Orientations in a Locked Subduction Zone at the Southern Hikurangi Margin, New Zealand

et al. 2017

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We analyze the orientation of the stress field in the southern Hikurangi subduction zone, New Zealand, using focal mechanism inversions, S wave splitting fast directions, and gravitational stresses. Here the oceanic Pacific plate is being obliquely subducted beneath the continental Australian plate in the New Zealand plate boundary zone. The study makes use of 399 earthquakes for focal mechanism inversion and 425 earthquakes for shear wave splitting analysis, located with a network of seismic stations spanning southern North Island. We distinguish between stresses in the Pacific plate (from focal mechanism inversion) and Australian plate (from S wave fast directions) and gravitational stresses, in three regions: Western, Central Basin, and Eastern. In the Western region, the principal axis of horizontal compression (SHmax) is oriented NE‐SW, parallel to the margin, in the upper Australian and lower Pacific plate. In the Central Basin, SHmax in the Australian plate is oriented NW‐SE, perpendicular to the margin; in the lower subducting Pacific plate SHmax is oriented NE‐SW. In the Eastern region, SHmax is oriented NE‐SW in the upper plate, while in the lower plate there is a change in orientation to NNW‐SSE. We interpret the stress orientations of the lower plate in the Western and Central Basin regions as a consequence of bending of the subducting plate. Sources of upper Australian plate stresses are likely to be bending stresses, gravitational stresses, and tectonic loading, with differing relative magnitudes across the study area.

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Section: Methodsmentioning

confidence: 99%

Stress Orientations in a Locked Subduction Zone at the Southern Hikurangi Margin, New Zealand

et al. 2017

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“…In contrast, we interpret the resistive zones as relatively cold brittle zones with a fluid deficit. We hypothesize that the conductive zone preferentially deforms, such that the static stress over Kyushu (Matsumoto et al 2015;Savage et al 2016) accumulates preferentially in proximal brittle resistive zones and subsequently causes large earthquakes. The concept of local stress accumulation has been proposed based on the results of previous magnetotelluric studies (e.g., Ogawa et al 2001;Ichihara et al 2008Ichihara et al , 2014Wannamaker et al 2009).…”

Section: Discussionmentioning

confidence: 99%

“…To investigate the relationship between the earthquakes and the resistivity structure in the study area, the hypocenters, which were relocated by manual readings of P-wave arrival times (Shimizu et al 2016), are plotted on the resistivity sections at depths of 8 and 12 km (Fig. 6).…”

Section: Discussionmentioning

confidence: 99%

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Seismicity controlled by resistivity structure: the 2016 Kumamoto earthquakes, Kyushu Island, Japan

Aizawa

Asaue

Koike

et al. 2017

Earth Planets Space

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The M JMA 7.3 Kumamoto earthquake that occurred at 1:25 JST on April 16, 2016, not only triggered aftershocks in the vicinity of the epicenter, but also triggered earthquakes that were 50-100 km away from the epicenter of the main shock. The active seismicity can be divided into three regions: (1) the vicinity of the main faults, (2) the northern region of Aso volcano (50 km northeast of the mainshock epicenter), and (3) the regions around three volcanoes, Yufu, Tsurumi, and Garan (100 km northeast of the mainshock epicenter). Notably, the zones between these regions are distinctively seismically inactive. The electric resistivity structure estimated from one-dimensional analysis of the 247 broadband (0.005-3000 s) magnetotelluric and telluric observation sites clearly shows that the earthquakes occurred in resistive regions adjacent to conductive zones or resistive-conductive transition zones. In contrast, seismicity is quite low in electrically conductive zones, which are interpreted as regions of connected fluids. We suggest that the series of the earthquakes was induced by a local accumulated stress and/or fluid supply from conductive zones. Because the relationship between the earthquakes and the resistivity structure is consistent with previous studies, seismic hazard assessment generally can be improved by taking into account the resistivity structure. Following on from the 2016 Kumamoto earthquake series, we suggest that there are two zones that have a relatively high potential of earthquake generation along the western extension of the MTL.

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“…Intense local seismicity and the dense seismic network in the Kumamoto source area (Figure b) provide a unique opportunity to study focal mechanism solutions (FMSs) of crustal earthquakes as well as spatial and temporal variations of the stress field. Previous studies have generally adopted one‐dimensional (1‐D) seismic velocity models to investigate the stress field in Kyushu (e.g., Matsumoto, Nakao, et al, ; Savage et al, ; Yoshida et al, ). However, many studies of seismic tomography have revealed strong seismic velocity variations in Kyushu, such as low‐velocity anomalies related to the arc magma and fluids in the crust and upper mantle wedge, and the subducting PHS slab that exhibits a strong high‐velocity anomaly (e.g., Liu & Zhao, , ; Z. W. Wang et al, ; Z. Wang & Zhao, , ; J. Wang & Zhao, ; Xia et al, ; Yu et al, ; Zhao, ; Zhao et al, ).…”

Section: Introductionmentioning

confidence: 99%

Stress Field in the 2016 Kumamoto Earthquake (M 7.3) Area

Zhao

et al. 2019

JGR Solid Earth

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We used 1‐D and 3‐D velocity models to determine focal mechanism solutions (FMSs) of 349 crustal earthquakes (M 2.7–7.3) and stress tensors in the source area of the 2016 Kumamoto earthquake (M 7.3) that occurred on the Futagawa‐Hinagu fault zone in Kyushu, Southwest Japan. There are some differences in the FMSs determined with the 1‐D and 3‐D velocity models. The use of the 3‐D velocity model leads to better results of stress tensors, which are determined by inverting the FMSs. The orientation of the minimum stress (σ3) axis is more accurately determined, which trends NNW‐SSE to N‐S nearly horizontally. In contrast, the axes of the maximum and intermediate stresses (σ1 and σ2) trend WSW‐ENE to E‐W with wide ranges. Significant spatiotemporal variations of the stress field are revealed in the Kumamoto source zone, indicating a small magnitude of deviatoric stress. The friction coefficient of the faults is estimated to be relatively small (~0.4), indicating that the seismogenic faults in central Kyushu are weak. The fault weakening may be caused by fluids beneath the source area and arc magma under the nearby Aso active volcano.

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Stress, strain rate and anisotropy in Kyushu, Japan

Cited by 54 publications

References 44 publications

Stress Orientations in a Locked Subduction Zone at the Southern Hikurangi Margin, New Zealand

Stress Orientations in a Locked Subduction Zone at the Southern Hikurangi Margin, New Zealand

Seismicity controlled by resistivity structure: the 2016 Kumamoto earthquakes, Kyushu Island, Japan

Stress Field in the 2016 Kumamoto Earthquake (M 7.3) Area

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