3-D resistivity imaging of the supercritical geothermal system in the Sengan geothermal region, NE Japan

Yamaya, Yusuke; Suzuki, Yota; Murata, Yoshinori; Okamoto, Kyosuke; Watanabe, Norihiro; Asanuma, Hiroshi; Häse, H.; Ogawa, Yasuo; Mogi, Toru; Ishizu, Keiichi; Uchida, Toshihiro

doi:10.1016/j.geothermics.2022.102412

Cited by 11 publications

(5 citation statements)

References 44 publications

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“…The shallow cap-like conductor (σ = 0.1-0.3 S/m), shown in Figure 4b under Aluto volcano down to depths of 1.5 km below the surface, and the underlying zone of decreased electrical conductivities (σ = 0.02 S/m) between the cap and the upper part of the magma ascent channel C2 are typical features of volcano-hosted, high-temperature geothermal systems (e.g., Bertrand et al, 2012;Omollo et al, 2022;Yamaya et al, 2022). The electrically conductive cap represents the argillic alteration zone, where electrically conductive clays are formed along the flow paths of circulating hot fluids on top of the convective hydrothermal reservoir (e.g., Pellerin et al, 1992).…”

Section: Geothermal Systemmentioning

confidence: 99%

Insights on the Interplay of Rifting, Transcrustal Magmatism and Formation of Geothermal Resources in the Central Segment of the Ethiopian Rift Revealed by 3‐D Magnetotelluric Imaging

et al. 2023

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The East African Rift system (EARS) is a prominent continental rift that shaped the landscape of East Africa, including the East African Plateau, rift valleys and numerous volcanoes. Rifting and rift-related volcanism in East Africa played a role in early human evolution (King & Bailey, 2006) and to this date affect the life of humans due to volcanic hazards (Biggs et al., 2021), but also by providing rift-associated natural resources, including geothermal energy resources (Benti et al., 2023;Burnside et al., 2021). A large number of studies, especially in the northern part of the EARS, which includes the Main Ethiopian Rift (MER), have provided a wealth of information Abstract The Main Ethiopian Rift is accompanied by extensive volcanism and the formation of geothermal systems, both having a direct impact on the lives of millions of inhabitants. Although previous studies in the region found evidence that asthenospheric upwelling and associated decompression melting provide melt to magmatic systems that feed the tectono-magmatic segments in the rift valley, there is a lack of geophysical models imaging these regional and local scale transcrustal structures. To address this challenge, we use the magnetotelluric method and image subsurface electrical conductivity to examine the magmatic roots of Aluto volcano, quantify and interpret the melt distribution in the crust considering established concepts of continental rifting processes and constrain the formed geothermal system. Specifically, we combined regional (maximum 30 × 120 km 2 ) and local (15 × 15 km 2 ) magnetotelluric data sets and obtained the first multi-scale 3-D electrical conductivity model of a segment of the central Main Ethiopian Rift. The model unravels a magma ponding zone with up to 7 vol. % melt at the base of the crust (30-35 km b.s.l.) in the western part of the rift and its connection to Aluto volcano via a fault-aligned transcrustal magma system. Melt accumulates at shallow crustal depths (≥4 km b.s.l.), thereby providing heat for Aluto's geothermal system. Our model suggests that different volcano-tectonic lineaments in the rift valley share a common melt source. The presented model provides new constraints on the melt distribution below a segment of the rift which is important for future geothermal developments and volcanic hazard assessments in the region.Plain Language Summary Continental rifting is a fundamental process of plate tectonics that breaks continents apart to ultimately form new oceans. The landscape of the Main Ethiopian Rift is characterized by abundant volcanism and hot springs, which indicate the presence of geothermal resources formed by magmatic heating of subsurface fluids. Here we present a new 3-D subsurface electrical conductivity image of the magmatic system and geothermal reservoir beneath the Aluto volcano in the Main Ethiopian Rift. The model allows us to estimate the amount and distribution of magmatic melt. This is the first model that provides a high-resolution image of the entire magmatic system below a centr...

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Section: Geothermal Systemmentioning

confidence: 99%

Insights on the Interplay of Rifting, Transcrustal Magmatism and Formation of Geothermal Resources in the Central Segment of the Ethiopian Rift Revealed by 3‐D Magnetotelluric Imaging

et al. 2023

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“…Several EM induction surveys have been conducted in strain concentration zones in Japan: the NKTZ (Goto et al., 2005; Ogawa & Honkura, 2004; Takakura et al., 1997; Usui et al., 2021; Uyeshima et al., 2005; Yoshimura et al., 2009), the SCZEJS (Toh et al., 2006), SCZGS (Ichihara et al., 2011), SCZOBR (Ichihara et al., 2014; Ishizu et al., 2022; Mishina, 2009; Ogawa et al., 2001, 2014; Yamaya et al., 2022), and Ishikari lowland (Yamaya et al., 2017). However, these studies did not investigate the regional three‐dimensional (3‐D) crustal structure in the SCZGS or the spatial differences in the strain concentration mechanism.…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Electrical Resistivity Structure Beneath a Strain Concentration Area in the Back‐Arc Side of the Northeastern Japan Arc

Usui,

Uyeshima,

Hase

et al. 2024

JGR Solid Earth

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Intraplate earthquakes occur more frequently in the Japanese islands than in other regions. Large intraplate earthquakes in the island arc preferentially occur in strain concentration zones detected by geological and geodetic studies. Crustal heterogeneity plays a crucial role in generating large intraplate earthquakes and strain concentrations. Thus, we elucidated the crustal heterogeneities beneath a strain concentration area on the back‐arc side of the northeastern Japan Arc based on electrical resistivity, which is sensitive to weak zones in the crust. By deploying wideband magnetotelluric surveys, we revealed the three‐dimensional electrical resistivity structure in the crust, suggesting the coexistence of two different types of strain‐concentration mechanisms in the strain‐concentration area. The shallow conductive layers and lower‐crustal conductors appear to act as low‐elastic‐modulus and low‐viscosity areas, respectively, and are responsible for the strain concentration. We found shallow and lower‐crustal conductors in the strain concentration zone revealed by geological studies. Those conductive areas are considered to act as mechanically weak zones and cause stress loading on the brittle pars of pre‐existing faults, resulting in large intraplate earthquakes. The resultant earthquakes presumably contribute to strain accumulation on a geological timescale. In addition, a spatial correlation between the epicenters of large intraplate earthquakes and edges of lower‐crustal conductors implies the contribution of the fluids in the lower crust to the generation of large earthquakes. We also identified vertical conductors ranging from the lower crust to Quaternary volcanoes, which may indicate trans‐crustal magmatic systems under these volcanoes.

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“…In Japan, supercritical geothermal uid may exist in several regions, such as Kakkonda in northeastern Japan ( 12,13 ) and the Kuju volcanic complex in northern Kyushu, southwestern Japan ( 14,15 ). In the Kakkonda eld, various studies (e.g., 12,16,17 ) have suggested that supercritical geothermal uids may be present in the core of a relatively aseismic, low-resistivity zone beneath depths of 3 km below sea level with a steep temperature gradient from ~ 380°C to 500°C.…”

Section: Introductionmentioning

confidence: 99%

Tracking supercritical geothermal fluid distribution from continuous seismic monitoring

Andajani

Tsuji

Ikeda

et al. 2023

Preprint

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Continuous seismic monitoring could play a pivotal role in deep geothermal energy exploration. We monitored seismicity near geothermal production areas of the Kuju volcanic complex with a dense seismic network and automated event detection. Most events were shallow (less than 3 km below sea level) and distributed along a boundary between regions of high and low resistivity and S-wave velocity, interpreted as a lithological boundary or related fracture zone. Deeper events located on top of subvertical conductors may reflect fracturing associated with magmatic fluid intrusion. We attribute a possible correlation between seismicity and heavy rainfall three days prior to increased pore pressure in pre-existing fractures. Our findings support the presence of supercritical geothermal fluids and demonstrate the importance of continuous seismic monitoring in supercritical geothermal energy exploration.

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3-D resistivity imaging of the supercritical geothermal system in the Sengan geothermal region, NE Japan

Cited by 11 publications

References 44 publications

Insights on the Interplay of Rifting, Transcrustal Magmatism and Formation of Geothermal Resources in the Central Segment of the Ethiopian Rift Revealed by 3‐D Magnetotelluric Imaging

Insights on the Interplay of Rifting, Transcrustal Magmatism and Formation of Geothermal Resources in the Central Segment of the Ethiopian Rift Revealed by 3‐D Magnetotelluric Imaging

Three‐Dimensional Electrical Resistivity Structure Beneath a Strain Concentration Area in the Back‐Arc Side of the Northeastern Japan Arc

Tracking supercritical geothermal fluid distribution from continuous seismic monitoring

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