The seismic velocity and attenuation structure beneath the Tatun volcanic area, Taiwan

Wen, Strong; Chang, Yi-Zen; Chen, Chau‐Huei; Chen, Yue‐Gau; Teng, Ta‐Liang

doi:10.1016/j.jseaes.2012.04.011

Cited by 9 publications

(6 citation statements)

References 37 publications

(52 reference statements)

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“…For the TPT, Fu et al [41] proposed that radon anomalies at the TPT station could be found when a small earthquake has hypocenters shallower than 15 km within 30 km of the monitoring station or when a large earthquake has deeper hypocenters (>20 km) at a greater distance (>45 km). In this paper, the similar anomalies in radon are also confirmed before the near-and far-field earthquakes, such as Events 6,7,8,10,17,18,20,21,23,24,27, e, g, and j. The preearthquake activities of the far-field events may be transmitted to the region below the TPT site along the major decollement (e.g., [55,56]) and can facilitate the release of soil gases when squeezed.…”

Section: Spatial Variation Of Relatedsupporting

confidence: 65%

“…The volumetric expansions of the EP around northern Taiwan then released the additional radiogenic gas from the crustal component. The increase in gamma rays can be attributed to the expansion around the YMSG that produced new fractures for gas and fluid migrations, potentially associated with the slow slip (e.g., Events 6,7,8,10,17,20,21,23,24,and 27). A similar explanation of the preseismic slow slip before the Tohoku earthquake was illustrated by Orihara et al [60].…”

Section: Spatial Variation Of Relatedmentioning

confidence: 78%

“…However, Yang et al [13,14] and Ohba et al [15] suggested that a magma chamber might still exist beneath the TVG area based on a high 3 He/ 4 He ratio from fumarolic gas and the high CO 2 /H 2 O ratio of magmatic components. Konstantinou et al [16] and Wen et al [17] proposed that magma chambers might exist at depths of 7 to 20 km as indicated by the seismicity characteristics and attenuation structure. Lin [18] proposed the presence of a deep magma reservoir in the lower crust using S-wave shadow and Pwave delay.…”

Section: Introductionmentioning

confidence: 99%

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Gamma Ray and Radon Anomalies in Northern Taiwan as a Possible Preearthquake Indicator around the Plate Boundary

Lee

Yang

et al. 2019

Geofluids

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Taiwan is tectonically situated in an oblique collision zone between the Philippine Sea Plate (PSP) and the Eurasian Plate (EP). Continuous observations of gamma rays at the Yangmingshan (YMSG) station and soil radon at the Tapingti (TPT) station were recorded in the volcanic area and around a major fault zone, respectively, in Taiwan for seismic studies. A number of anomalous high gamma ray counts and radon concentrations at certain times were found. It is noted that significant increases of soil radon concentrations were observed and followed by the increase in gamma rays a few days to a few weeks before earthquakes that occurred in northeastern Taiwan. Earthquakes such as these are usually related to the subduction of the PSP beneath the EP to the north along the subduction zone in northern Taiwan (e.g., ML=6.4, April 20, 2015). It is suggested that the preseismic activity may be associated with slow geodynamic processes at the subduction interface, leading to the PSP movement triggering radon enhancements at the TPT station. Furthermore, the further movement of the PSP might be blocked by the EP, with the accumulated elastic stress resulting in the increase of gamma rays due to the increase in porosity and fractures below the YMSG station. The continuous monitoring of the multiple parameters can improve the understanding of the relationship between the observed radon and gamma ray variations and the regional crustal stress/strain in north and northeastern Taiwan.

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Section: Spatial Variation Of Relatedsupporting

confidence: 65%

Section: Spatial Variation Of Relatedmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Gamma Ray and Radon Anomalies in Northern Taiwan as a Possible Preearthquake Indicator around the Plate Boundary

Lee

Yang

et al. 2019

Geofluids

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“…Lee et al (2008) repeatedly observed the fumarolic gases at TVG, and detected a co-seismic change in the 3 He/ 4 He ratio. Recently, a seismic tomography study from Wen et al (2012) showed the existence of a tube-shaped, highly fractured ancient magma passage with high seismic velocities that parallel the Chinshan fault and a magma passage that extends to the southeast at a depth of about 20 km. This structure suggests a plutonic intrusion passage beneath TVG that may have been associated with the earlier subduction of the Philippine Sea plate.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

He, Ar, N and C isotope compositions in Tatun Volcanic Group (TVG), Taiwan: Evidence for an important contribution of pelagic carbonates in the magmatic source

Roulleau

Sano

Takahata

et al. 2015

Journal of Volcanology and Geothermal Research

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“…This finding excludes that P-wave delays can be served as evidence of the present of a magma reservoir. The most intuitive answer to the P-wave delays is that the seismic wave velocity on the footwall (west) of the Shanchiao fault is smaller than that on the hanging wall 12 , 21 , 25 . For example, the ray path from the Shanchiao fault to the station VO06 is 41.3 km for EQ2.…”

Section: Discussionmentioning

confidence: 99%

Dense seismic arrays deny a massive magma chamber beneath the Taipei metropolis, Taiwan

Yeh

Wang

Wen

2021

Sci Rep

Self Cite

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Several recent studies suggest that the Tatun Volcano Group (TVG) in the Taipei metropolis of Taiwan is still active with a mappable magma chamber beneath it. Here we report new seismic evidence from dense seismic arrays in northern Taiwan to refute the presence of a massive magma chamber. We investigated two near Taipei earthquakes with focal depths of ~ 140 km. We found that all the waveforms exhibited distinct S waves even when they traversed across the previously postulated magma chamber. Instead, the S-wave shadows found in the previous study may result from seismic waves traveling through a magma diapir above the subducting Philippine Sea Plate offshore northern Taiwan. Moreover, we found the P-wave delay increased with hypocentral distance when the seismic waves propagated through the footwall (west side) of the Shanchiao fault, regardless of whether they traversed across the postulated magma chamber. Our study results also indicate no abnormal attenuation when seismic rays traversed across the postulated magma chamber. Furthermore, the average $${Q}_{P}/{Q}_{S}$$ Q P / Q S ratio around the TVG is less than 1, which implies that scattering attenuation is dominant. We conclude that a highly fractured rock body is beneath the TVG with a tiny fraction of magma instead of a massive magma chamber. Without sufficient magma supply, the TVG may stay dormant (except for small phreatic eruptions).

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The seismic velocity and attenuation structure beneath the Tatun volcanic area, Taiwan

Cited by 9 publications

References 37 publications

Gamma Ray and Radon Anomalies in Northern Taiwan as a Possible Preearthquake Indicator around the Plate Boundary

Gamma Ray and Radon Anomalies in Northern Taiwan as a Possible Preearthquake Indicator around the Plate Boundary

He, Ar, N and C isotope compositions in Tatun Volcanic Group (TVG), Taiwan: Evidence for an important contribution of pelagic carbonates in the magmatic source

Dense seismic arrays deny a massive magma chamber beneath the Taipei metropolis, Taiwan

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