Seismic velocity structure in and around the Naruko volcano, NE Japan, and its implications for volcanic and seismic activities

Okada, Tomomi; Matsuzawa, Toru; Nakajima, Jun; Uchida, Naoki; Yamamoto, Mare; Hori, Shuichiro; Kono, Toru; Nakayama, Takashi; Hirahara, Satoshi; Hasegawa, Akira

doi:10.1186/1880-5981-66-114

Cited by 25 publications

(46 citation statements)

References 31 publications

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“…At greater depths, the LVZs beneath Naruko Volcano and Onikobe Caldera shift southwestward and southward, respectively. While the distinct LVZ beneath Onikobe Caldera has been recognized in previous studies (e.g., Nakajima and Hasegawa 2003;Okada et al 2014), the LVZ beneath Naruko Volcano had previously been resolved only by a magnetotelluric survey (Ogawa et al 2014). We also found a LVZ beneath Mt.…”

Section: Methodssupporting

confidence: 50%

“…This LVZ extends approximately 15 km southward at depths of 5 and 7 km. The LVZs in the south and southeast correspond to a sedimentary basin as mentioned in Okada et al (2014). To discuss the LVZs mentioned above, we compared our results with the distribution of aftershocks of the 2008 earthquake and S-wave reflectors.…”

Section: Methodsmentioning

confidence: 99%

“…Several seismic tomography studies have been carried out in and around the focal area, and distinct low-velocity zones (LVZ) with high P-wave velocity (V p )/V s have been recognized in the lower crust beneath volcanoes (Nakajima and Hasegawa 2003;Okada et al 2010;Okada et al 2012;Okada et al 2014). They are considered to be molten magma originating from the upwelling flows in the mantle wedge.…”

Section: Introductionmentioning

confidence: 99%

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Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

Tamura

Okada

2016

Earth Planet Sp

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To understand the earthquake generation in volcanic areas, it is important to investigate the presence of geofluids in the uppermost crust. We applied ambient noise tomography to the Naruko/Onikobe volcanic area and constructed a detailed 3-D S-wave velocity (V s ) model using continuous records from a dense seismic network and surrounding stations. The low-velocity zones were found beneath Naruko Volcano, Onikobe Caldera, and Mt. Kurikoma. The low-velocity zone beneath Onikobe Caldera may correspond to a magma reservoir, which is also characterized by surrounding S-wave reflectors. The molten magma originates from the upwelling flows in the mantle wedge. We also conducted the relocation of aftershocks of the 2008 Iwate-Miyagi Nairiku earthquake by double-difference tomography based on the obtained velocity model. Beneath Mt. Kurikoma, aftershock distribution delineates one of the unfavorably oriented fault planes of the main shock, which implies that the low-velocity zone around the fault plane is related to the presence of overpressurized fluid.

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Section: Methodssupporting

confidence: 50%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

Tamura

Okada

2016

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“…Three-dimensional (3D) seismic velocity heterogeneities have enhanced our understanding of spatial variations in the elastic properties beneath high-strain-rate zones (e.g., Nakajima and Hasegawa 2007;Okada et al 2014). However, the anelasticity associated with such zones is poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Anelastic properties beneath the Niigata–Kobe Tectonic Zone, Japan

Nakajima

Matsuzawa

2017

Earth Planets Space

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We estimate the three-dimensional (3D) P-wave attenuation structure beneath the Niigata-Kobe Tectonic Zone (NKTZ), central Japan, using high-quality waveform data from a large number of stations. The obtained results confirm the segmentation of the NKTZ into three regions, as suggested by 3D seismic velocity models, and reveal characteristic structures related to surface deformation, shallow subduction of the Philippine Sea slab, and magmatism. The lower crust beneath the NKTZ west of the Itoigawa-Shizuoka Tectonic Line (ISTL) is overall characterized by distinct high attenuation, whereas the upper crust shows marked high attenuation to the east of the ISTL. Differences in the depths of anelastically weakened parts of the crust probably result in a first-order spatial variation in surface deformation, forming wide (width of ~100 km) and narrow (width of 25-40 km) deformation zones on the western and eastern sides of the ISTL, respectively. Many M ≥ 6.5 earthquakes occur in the upper crust where seismic attenuation in the underlying lower crust varies sharply, suggesting that spatial variations in rates of anelastic deformation in the lower crust result in stress concentration in the overlying brittle crust. We interpret a moderate-to low-attenuation zone located in the lower crust at the northeast of Biwa Lake to reflect low-temperature conditions that are developed locally as a result of shallow subduction of the cold Philippine Sea slab.

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“…They found a southward-dipping, sub-vertical conductor that may imply the presence of geofluids just below the volcano. Okada et al (2014) found seismic low-velocity zones beneath the same volcano and in the aftershock region of the 2008 Iwate-Miyagi Nairiku earthquake, both of which can be attributed to the presence of geofluids. The former, having a diameter of 10 to 20 km, resides in the lower crust.…”

Section: Geofluids Detected With Magnetotelluric and Seismic Observatmentioning

confidence: 99%

Special issue ‘Geofluid processes in subduction zones and mantle dynamics’

et al. 2015

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Seismic velocity structure in and around the Naruko volcano, NE Japan, and its implications for volcanic and seismic activities

Cited by 25 publications

References 31 publications

Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

Anelastic properties beneath the Niigata–Kobe Tectonic Zone, Japan

Special issue ‘Geofluid processes in subduction zones and mantle dynamics’

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