Electromagnetic heterogeneity of the seismogenic region of 1962 M6.5 Northern Miyagi Earthquake, northeastern Japan

Mitsuhata, Yuji; Ogawa, Yasuo; Mishina, Masaaki; Kono, Toru; Yokokura, Takanobu; Uchida, Toshihiro

doi:10.1029/2001gl013079

Cited by 61 publications

(32 citation statements)

References 15 publications

(4 reference statements)

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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: 82%

“…The concept is similar to the hypothesis of Iio et al (2002) who assumed that the lower crust had a deformable weak zone. In addition, our results suggest that fluids supplied from conductive zones to nearby resistive zones can promote earthquake occurrences (e.g., Mitsuhata et al 2001;Ogawa et al 2001;Yoshimura et al (Yamashina and Murai 1975) are also overlain on the profiles. Because the hypocentral depths of these two earthquakes were not determined, they are plotted on both profiles.…”

Section: Discussionmentioning

confidence: 85%

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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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Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 85%

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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“…Often, seismicity seems to be confined along one edge of a FZC, indicating that the conductive region is too weak for brittle faulting [Unsworth et al, 1999;Bedrosian et al, 2002]. Alternatively, the seismicity may be a result of seepage/migration of fluids from the fluid-filled conductive zones to less permeable regions of the crust, where they trigger an earthquake [Mitsuhata et al, 2001]. Finally, fluids transport solutes and have control on sealing mechanisms of the fault fracture mesh, which may lead to strength recovery of the fault system.…”

Section: Comparison Of Upper Crustal Fault Zone Studiesmentioning

confidence: 99%

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

2004

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[1] Large-scale strike-slip fault zones are often imaged as electrically conductive structures in the brittle crust. However, the relationship of conductivity and internal architecture of the fault zone remains largely unclear. This paper presents results of a study designed to compare the record of structural deformation across a fault zone with its electrical conductivity image. Two high-resolution magnetotelluric profiles trend perpendicularly across the West fault, a branch of the Precordilleran fault system in northern Chile. The magnetotelluric and geomagnetic response functions in the frequency range from 1000 Hz to 0.1 Hz clearly image a fault zone conductor (FZC) about 350 m wide and 1500 m deep, trending along the surface trace of the fault. The position of the FZC and its geometric properties (width, dip) correlate with a region of intense fluid alteration and the orientation of fault-related damage elements (minor faults, fractures). According to estimates of fluid salinity and rock porosity, the conductivity anomaly results from meteoric water penetrating into a permeable zone. This suggests that the increase in electrical conductivity is causally related to a mesh of minor faults and fractures, acting as a pathway for fluids. The FZC reflects the central and most fractured part of the damage zone. In view of similar published magnetotelluric studies, we infer a dependency of a fault's state of activity and the characteristics of the FZC such as its conductance, width, and depth extent. Ongoing deformation is the controlling factor for maintaining a permeable and electrically conductive fracture network.

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“…Electromagnetic imaging of subsurface resistivity structure has made important contributions in the study of active tectonics. The tectonic setting of Japan is quite similar to Taiwan and was imaged by a number of magnetotelluric studies (Mitsuhata et al 2001;Ogawa et al 2001;Ogawa and Honkura 2004). This work revealed that fluids are widely distributed in the mid-crust, and related to seismicity and surface deformation.…”

Section: Introductionmentioning

confidence: 84%

Crustal Resistivity Anomalies Beneath Central Taiwan Imaged by a Broadband Magnetotelluric Transect

Chen¹,

Chen²,

Chiang³

et al. 2007

Terr. Atmos. Ocean. Sci.

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Electromagnetic heterogeneity of the seismogenic region of 1962 M6.5 Northern Miyagi Earthquake, northeastern Japan

Cited by 61 publications

References 15 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

Correlation of electrical conductivity and structural damage at a major strike‐slip fault in northern Chile

Crustal Resistivity Anomalies Beneath Central Taiwan Imaged by a Broadband Magnetotelluric Transect

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