Sanyi‐Puli conductivity anomaly in NW Taiwan and its implication for the tectonics of the 1999 Chi‐Chi earthquake

Chen, Chien Chih; Chen, Chow Son

doi:10.1029/2001gl013890

Cited by 11 publications

(7 citation statements)

References 15 publications

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“…From our results, the regional stress pattern appears to be closely related to the structural configuration of the LMH, which presumably corresponds to a relatively rigid zone containing mostly igneous rocks [ Hsu et al , 2008]. For examples, the eastern front of LMH roughly marks the western end of the predominantly thrust‐type regime beneath central Taiwan (Figure 7), whereas the northern limit of the LMH is associated with a strike‐slip stress regime (Figure 7d), roughly bounded by the Sanyi‐Puli transfer fault zone (a linear NW–SE left‐lateral transfer fault system characterized by high electrical conductivity [ Chen and Chen , 2002; Deffontaines et al , 1994]). Our observation provides no constraint on the stress regime in the western part of LMH due to the lack of focal mechanism data offshore west of Taiwan (Figures 2, 3d and 3e).…”

Section: Stress Inversion Results and Interpretationsmentioning

confidence: 99%

Spatial variation of the crustal stress field along the Ryukyu‐Taiwan‐Luzon convergent boundary

Kao

Hsu

et al. 2010

J. Geophys. Res.

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[1] We applied an improved stress inversion method to a comprehensive data set of earthquake focal mechanisms to depict the pattern of crustal stress along the western convergent boundary of the Philippine Sea plate. Our results indicate that the crustal stress along the Ryukyu fore arc is segmented with boundaries at or near the places of seamount subduction, including the Tokara channel. An extensional stress regime is observed along the entire Ryukyu back arc, implying that back-arc rifting may have extended northward to Kyushu. A triangular area near the southernmost terminus of the Ryukyu arc is characterized by a unique stress signature. The eastern boundary of this Ryukyu-Taiwan Stress Transition coincides with the 123°E meridian where the Gagua ridge intercepts the Ryukyu trench; whereas its western boundary agrees remarkably well with the border between the postcollision and waning-collision domains in northern Taiwan. The Taiwan collision zone is dominated by compression that rotates locally according to the structural configuration of the Lukang Magnetization High (LMH), suggesting that the LMH may be critical in controlling the local stress distribution. The stress signature of the Luzon arc-Taiwan collision reaches as far south as 19.5°N. The tectonic stress along the Manila trench-Luzon fore arc is dominated by a complex regime of extension that cannot be explained by simple plate bending or in-slab membrane stress. Since this extensional regime is observed only south of ∼22°N, it probably marks the northern limit of the contemporary boundary between the subduction along the Manila trench and the collision in Taiwan.

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Section: Stress Inversion Results and Interpretationsmentioning

confidence: 99%

Spatial variation of the crustal stress field along the Ryukyu‐Taiwan‐Luzon convergent boundary

Kao

Hsu

et al. 2010

J. Geophys. Res.

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“…The exceptionally low shear stress suggests the possible existence of fluid. The tomography study of Wu et al (2007) suggested a high Vp / Vs zone at 9 km depth beneath the northern portion of the Chelungpu‐fault and Chen & Chen (2002) analysed magnetotelluric (MT) data in the northern part of the Chelungpu‐fault concluded that a low resistivity zone exists at 10 km depth beneath the northern portion of the Chelungpu‐fault, indicating the possible existence of fluid in the detachment. In addition to that, as shown earlier, the seismicity in the detachment also occurs in earthquake clusters.…”

Section: Discussionmentioning

confidence: 99%

Observation and scaling of microearthquakes from the Taiwan Chelungpu-fault borehole seismometers

Lin¹,

Fong²,

Oye

2012

Geophysical Journal International

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SUMMARY Microearthquakes with magnitude down to 0.3 were detected by the Taiwan Chelungpu‐fault Drilling Project Borehole Seismometers (TCDPBHS). Despite the large coseismic slip of 12 m at the drill site during the 1999 Chi–Chi earthquake, our studies show very little seismicity near the TCDPBHS drill site 6 yr after the Chi–Chi main shock. The microearthquakes clustered at a depth of 9–12 km, where the Chelungpu thrust fault turns from a 30° dipping into the horizontal decollement of the Taiwan fold‐and‐thrust tectonic structure. Continuous GPS surveys did not observe post‐slip deformation at the larger slip region and no seismicity was observed near the drill site. Therefore we suggest that the thrust belt above the decollement is locked during this interseismic period. We further investigated source parameters of 242 microearthquakes by fitting ω−2‐shaped Brune source spectra to our observation data using a frequency‐independent Q model. We find that the static stress drop increases significantly with increasing seismic moment. However, due to the intense debate on this topic of scaling‐relations and the related self‐similarity of earthquakes, we further improve the data analysis and correct for path and site effects using the Projected Landweber Deconvolution (PLD) method for events within some clusters. The PLD method analyses the source time functions of the larger and the smaller event by an iterative technique. As a result we received source dimensions and stress drops of larger events including path and site effect corrections. The results from the PLD method are less scattered and also show a positive relation between static stress drop and seismic moment. We find a similar positive trend for the apparent stress scaling with seismic moment.

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“…We propose that this morphological depression is also related to the Peikang horst. The Sanyi‐Puli strike‐slip fault zone [ Chen and Chen , 2002; Mouthereau et al , 2002] and the alignment of microseismic activity to the south of the Sun‐Moon Lake seismic gap embayment [see Dominguez et al , 2003, Figure 2] may reflect also some indentation process. An age of ∼ 1.1 Ma may be assigned to this topographic depression: the synorogenic Toukoshan formation, initially deposited in the foreland, is present throughout the whole Puli basin (Figures 5 and 11) and has been subsequently folded.…”

Section: Kinematics Of Deformation Across the Taiwanese Rangementioning

confidence: 99%

Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills

2006

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[1] The Taiwanese range has resulted from the collision between the Luzon volcanic arc and the Chinese continental margin, which started about 6.5 Myr ago in the north, and has since propagated southward. The building of the range has been recorded in the spatiotemporal evolution of the foreland basin. We analyze this sedimentary record to place some constraints on the kinematics of crustal deformation. The flexure of the foreland under the load of the growing wedge started with a 1.5 Myr long phase of rapid subsidence and sedimentation, which has migrated southward over the last 3.5 Myr at a rate of 31 +10/À5 mm/yr, reflecting the structural evolution of the range and the growth of the topography during the oblique collision. Isopachs from the Toukoshan ($0 to 1.1 Ma) and Cholan ($1.1 to 3.3 Ma) formations, as well as the sedimentation rates retrieved from a well on the Pakuashan anticline, indicate that the foreland basement has been moving toward the center of mass of the orogen by $45-50 mm/yr during the development of the basin. From there, we estimate the long-term shortening rate across the range to 39.5-44.5 mm/yr. By considering available data on the thrust faults of the foothills of central Taiwan, we show that most (if not all) the shortening across the range is accommodated by the most frontal structures, with little if any internal shortening within the wedge. The range growth appears therefore to have been essentially sustained by underplating rather than by frontal accretion. In addition, only the upper $7 to 9 km of the underthrusted crust participates to the growth of the orogen. This requires that a significant amount of the Chinese passive margin crust is subducted beneath the Philippine Sea plate.Citation: Simoes, M., and J. P. , Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills,

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Sanyi‐Puli conductivity anomaly in NW Taiwan and its implication for the tectonics of the 1999 Chi‐Chi earthquake

Cited by 11 publications

References 15 publications

Spatial variation of the crustal stress field along the Ryukyu‐Taiwan‐Luzon convergent boundary

Spatial variation of the crustal stress field along the Ryukyu‐Taiwan‐Luzon convergent boundary

Observation and scaling of microearthquakes from the Taiwan Chelungpu-fault borehole seismometers

Investigating the kinematics of mountain building in Taiwan from the spatiotemporal evolution of the foreland basin and western foothills

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