Earthquake doublet in an active shear zone, southwest Japan: Constraints from geophysical and geochemical findings

Umeda, Koji; Asamori, Koichi; Makuuchi, Ayumu; Kobori, Kazuo

doi:10.1016/j.tecto.2014.07.025

Cited by 4 publications

(2 citation statements)

References 74 publications

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“…This study shows that the seismogenic zones correspond approximately to resistive zones lying adjacent to conductive zones, or to the conductive-resistive transition zone. These results are consistent with previous magnetotelluric studies conducted across the epicenters of large (>M 6) inland earthquakes (Mitsuhata et al 2001;Ogawa et al 2001;Tank et al 2003Tank et al , 2005Kasaya and Oshiman 2004;Ichihara et al 2008Ichihara et al , 2014Yoshimura et al 2008;Kaya et al 2009;Umeda et al 2011Umeda et al , 2014Chandrasekhar et al 2012) with the exception that aftershocks occur in a thick sedimentary layer (Uyeshima et al 2005). Note here that the dense magnetotelluric observations occasionally image localized subvertical conductors beneath the active faults (e.g., Unsworth et al 1997;Wannamaker et al 2002;Becken et al 2008;Ikeda et al 2013;Sass et al 2014).…”

Section: Discussionsupporting

confidence: 91%

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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Section: Discussionsupporting

confidence: 91%

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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“…An example is the earthquake doublet, which is defined as a pair of large-magnitude events that have small magnitude differences, spatial separation, and temporal separation between each other (Umeda et al, 2014;Astiz and Kanamori, 1984;Lay and Kanamori, 1980). If many earthquakes occur in a manner of clustering together in time and space they can be called clustering earthquakes (Zhuang and Ogata, 2004;Barenblatt et al, 1981).…”

Section: Introductionmentioning

confidence: 99%

An evaluation of reverse-time imaging of clustering earthquakes

et al. 2015

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Clustering earthquakes refer to the seismic events that occur closely with each other in time and space. Because their overlapping waveform records make it difficult to pick the first arrivals, the hypocenters of clustering earthquakes cannot be determined accurately by traveltime location methods. Here we apply a reverse-time imaging (RTI) method to map clustering earthquakes. Taking the advantage of directly using waveforms, the RTI method is capable to map either a single small earthquake or some densely distributed clustering earthquakes beneath a 2-D seismic array. In 3-D case the RTI method is successfully applied to locate the long-offset doublet earthquakes using the data from a set of sparsely distributed surface stations. However, for the same acquisition geometry, the RTI encounters challenges in mapping densely distributed clustering earthquakes. While it is obvious that improving the mapping of clustering earthquakes requires a denser receiver network with wider range of illumination angles, it is necessary to verify the actual resolution of the RTI method with synthetic data. In our study area in the Three Gorges region, our tests in 3-D case suggest that some events beneath the linear aligned sub-arrays have reasonable resolution.

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Heterogeneous b-value Distributions Measured Over an Extensive Region from the Northern Okinawa Trough to Southern Kyushu Island, Japan

Chiba

2022

Pure Appl. Geophys.

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Spatiotemporal b-value maps are presented for an extensive region from the northern Okinawa trough to off southern Kyushu Island, Japan. This region shows high seismic activity associated with a tectonic setting characterized by seafloor spreading caused by the opening of a back-arc basin in the Ryukyu arc–trench system and the presence of a left-lateral shear zone on southern Kyushu Island. The obtained spatial and temporal distributions of b-value for the analyzed period are highly heterogeneous, reflecting the influence of the tectonic features and processes of the region. A comparison of the results with other geophysical observations suggests deep fluids associated with mantle upwelling below the seismogenic layer are the dominant control on the observed b-value variations. In addition, the hypocentral area of the largest earthquake (M7.1), which occurred in 2015, corresponds approximately to a region with low b-values (b = 0.5–0.7). Another region with low b-values (b = 0.5–0.7) occurs in the west of the analyzed region off southern Kyushu Island, where the occurrence of large-magnitude events is not clearly recognized. During the analysis period, there were few moderate to large earthquakes in the analyzed region. Furthermore, some active faults that have the potential to generate large earthquakes of ~ M7 are located in those parts of the analyzed region with low b-values. These findings suggest a high likelihood of nucleation of large earthquakes in the focal region.

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Earthquake doublet in an active shear zone, southwest Japan: Constraints from geophysical and geochemical findings

Cited by 4 publications

References 74 publications

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

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

An evaluation of reverse-time imaging of clustering earthquakes

Heterogeneous b-value Distributions Measured Over an Extensive Region from the Northern Okinawa Trough to Southern Kyushu Island, Japan

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