Geometry and structure of northern surface ruptures of the 1999 Mw = 7.6 Chi-Chi Taiwan earthquake: Influence from inherited fold belt structures

Jian Cheng Lee, Hao Tsu Chu, Jacques Angelier, Yu Chang Chan, Jyr Ching Hu, Chia Yu Lu, Ruey-Juin Rau

Research output: Contribution to journalArticle

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Abstract

Surface ruptures associated with the 1999 Mw = 7.6 Chi-Chi earthquake in central western Taiwan have been characterised by mapping along the northern fault-segment. The earthquake occured on the reactivated Chelungpu fault in the frontal portion of the thin-skinned Taiwan fold-and-thrust belt. The N-S trending Chelungpu fault is a 90-km-long major west-verging thrust, which principally slips within, and parallel to, bedding of the Pliocene Chinshui Shale. In the northern segment of the earthquake fault trace, that we name the Shihkang-Shangchi fault zone, the surface ruptures turn to an E-W strike and produce a series of thrust-and-backthrust pop-ups, about 15 km long, forming several discontinuous subsegments distributed within a broad regional Pliocene syncline. The northern fault segments activated during the Chi-Chi earthquake, in the area where the displacement is largest, not only display anomalous trends and a variety of mechanisms, but also raise a major problem of structural inheritance. Detailed field investigation and kinematic analysis indicate that the surface ruptures in the Shihkang-Shangchi fault zone are the result of dip-slip thrusting, occasionally with a minor strike-slip component. The surface ruptures emerge at the surface from bedding-parallel thrusts on both limbs of the regional south-plunging syncline. In the middle part of the syncline, bedding-parallel thrusts are connected by thrusts that cross-cut beds. The surface ruptures also reactivate a NE-SW trending anticline (Diaoshenshan), with west-vergent thrust on the backlimb and east-vergent backthrust on the forelimb. This anticline is undergoing uplift by breaking through the regional N-S trending syncline. Combining GPS measurements, seismological data, and geological analyses, we propose a kinematic model with a 3-D fault surface for the 1999 earthquake in the area of the northern termination. We highlight the influence of both the local and regional structures (bedding parallel slip, pre-existing faults and folds) on the development of the earthquake rupture, and hence the role of the structural inheritance. We conclude that the south-plunging regional Pliocene syncline in fact acts as a slip/strain guide for the northern termination of the Chelungpu thrust. The Pliocene Chinshui Shale, as a major source of weakness within the syncline, has strongly influenced the pattern of slip surface during the 1999 earthquake rupture. We interpret the large vertical displacement along the northern segment as the fault rupture occuring over a surface whose radius of curvature tightens toward the north around the core of the syncline.

Original languageEnglish
Pages (from-to)173-192
Number of pages20
JournalJournal of Structural Geology
Volume24
Issue number1
DOIs
Publication statusPublished - 2002 Jan 1

Fingerprint

fold belt
syncline
rupture
thrust
geometry
earthquake
Pliocene
earthquake rupture
anticline
fault zone
shale
kinematics
dip-slip fault
fold and thrust belt
fault plane
curvature
limb
GPS
uplift
fold

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

Lee, Jian Cheng ; Chu, Hao Tsu ; Angelier, Jacques ; Chan, Yu Chang ; Hu, Jyr Ching ; Lu, Chia Yu ; Rau, Ruey-Juin. / Geometry and structure of northern surface ruptures of the 1999 Mw = 7.6 Chi-Chi Taiwan earthquake : Influence from inherited fold belt structures. In: Journal of Structural Geology. 2002 ; Vol. 24, No. 1. pp. 173-192.
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abstract = "Surface ruptures associated with the 1999 Mw = 7.6 Chi-Chi earthquake in central western Taiwan have been characterised by mapping along the northern fault-segment. The earthquake occured on the reactivated Chelungpu fault in the frontal portion of the thin-skinned Taiwan fold-and-thrust belt. The N-S trending Chelungpu fault is a 90-km-long major west-verging thrust, which principally slips within, and parallel to, bedding of the Pliocene Chinshui Shale. In the northern segment of the earthquake fault trace, that we name the Shihkang-Shangchi fault zone, the surface ruptures turn to an E-W strike and produce a series of thrust-and-backthrust pop-ups, about 15 km long, forming several discontinuous subsegments distributed within a broad regional Pliocene syncline. The northern fault segments activated during the Chi-Chi earthquake, in the area where the displacement is largest, not only display anomalous trends and a variety of mechanisms, but also raise a major problem of structural inheritance. Detailed field investigation and kinematic analysis indicate that the surface ruptures in the Shihkang-Shangchi fault zone are the result of dip-slip thrusting, occasionally with a minor strike-slip component. The surface ruptures emerge at the surface from bedding-parallel thrusts on both limbs of the regional south-plunging syncline. In the middle part of the syncline, bedding-parallel thrusts are connected by thrusts that cross-cut beds. The surface ruptures also reactivate a NE-SW trending anticline (Diaoshenshan), with west-vergent thrust on the backlimb and east-vergent backthrust on the forelimb. This anticline is undergoing uplift by breaking through the regional N-S trending syncline. Combining GPS measurements, seismological data, and geological analyses, we propose a kinematic model with a 3-D fault surface for the 1999 earthquake in the area of the northern termination. We highlight the influence of both the local and regional structures (bedding parallel slip, pre-existing faults and folds) on the development of the earthquake rupture, and hence the role of the structural inheritance. We conclude that the south-plunging regional Pliocene syncline in fact acts as a slip/strain guide for the northern termination of the Chelungpu thrust. The Pliocene Chinshui Shale, as a major source of weakness within the syncline, has strongly influenced the pattern of slip surface during the 1999 earthquake rupture. We interpret the large vertical displacement along the northern segment as the fault rupture occuring over a surface whose radius of curvature tightens toward the north around the core of the syncline.",
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Geometry and structure of northern surface ruptures of the 1999 Mw = 7.6 Chi-Chi Taiwan earthquake : Influence from inherited fold belt structures. / Lee, Jian Cheng; Chu, Hao Tsu; Angelier, Jacques; Chan, Yu Chang; Hu, Jyr Ching; Lu, Chia Yu; Rau, Ruey-Juin.

In: Journal of Structural Geology, Vol. 24, No. 1, 01.01.2002, p. 173-192.

Research output: Contribution to journalArticle

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T1 - Geometry and structure of northern surface ruptures of the 1999 Mw = 7.6 Chi-Chi Taiwan earthquake

T2 - Influence from inherited fold belt structures

AU - Lee, Jian Cheng

AU - Chu, Hao Tsu

AU - Angelier, Jacques

AU - Chan, Yu Chang

AU - Hu, Jyr Ching

AU - Lu, Chia Yu

AU - Rau, Ruey-Juin

PY - 2002/1/1

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N2 - Surface ruptures associated with the 1999 Mw = 7.6 Chi-Chi earthquake in central western Taiwan have been characterised by mapping along the northern fault-segment. The earthquake occured on the reactivated Chelungpu fault in the frontal portion of the thin-skinned Taiwan fold-and-thrust belt. The N-S trending Chelungpu fault is a 90-km-long major west-verging thrust, which principally slips within, and parallel to, bedding of the Pliocene Chinshui Shale. In the northern segment of the earthquake fault trace, that we name the Shihkang-Shangchi fault zone, the surface ruptures turn to an E-W strike and produce a series of thrust-and-backthrust pop-ups, about 15 km long, forming several discontinuous subsegments distributed within a broad regional Pliocene syncline. The northern fault segments activated during the Chi-Chi earthquake, in the area where the displacement is largest, not only display anomalous trends and a variety of mechanisms, but also raise a major problem of structural inheritance. Detailed field investigation and kinematic analysis indicate that the surface ruptures in the Shihkang-Shangchi fault zone are the result of dip-slip thrusting, occasionally with a minor strike-slip component. The surface ruptures emerge at the surface from bedding-parallel thrusts on both limbs of the regional south-plunging syncline. In the middle part of the syncline, bedding-parallel thrusts are connected by thrusts that cross-cut beds. The surface ruptures also reactivate a NE-SW trending anticline (Diaoshenshan), with west-vergent thrust on the backlimb and east-vergent backthrust on the forelimb. This anticline is undergoing uplift by breaking through the regional N-S trending syncline. Combining GPS measurements, seismological data, and geological analyses, we propose a kinematic model with a 3-D fault surface for the 1999 earthquake in the area of the northern termination. We highlight the influence of both the local and regional structures (bedding parallel slip, pre-existing faults and folds) on the development of the earthquake rupture, and hence the role of the structural inheritance. We conclude that the south-plunging regional Pliocene syncline in fact acts as a slip/strain guide for the northern termination of the Chelungpu thrust. The Pliocene Chinshui Shale, as a major source of weakness within the syncline, has strongly influenced the pattern of slip surface during the 1999 earthquake rupture. We interpret the large vertical displacement along the northern segment as the fault rupture occuring over a surface whose radius of curvature tightens toward the north around the core of the syncline.

AB - Surface ruptures associated with the 1999 Mw = 7.6 Chi-Chi earthquake in central western Taiwan have been characterised by mapping along the northern fault-segment. The earthquake occured on the reactivated Chelungpu fault in the frontal portion of the thin-skinned Taiwan fold-and-thrust belt. The N-S trending Chelungpu fault is a 90-km-long major west-verging thrust, which principally slips within, and parallel to, bedding of the Pliocene Chinshui Shale. In the northern segment of the earthquake fault trace, that we name the Shihkang-Shangchi fault zone, the surface ruptures turn to an E-W strike and produce a series of thrust-and-backthrust pop-ups, about 15 km long, forming several discontinuous subsegments distributed within a broad regional Pliocene syncline. The northern fault segments activated during the Chi-Chi earthquake, in the area where the displacement is largest, not only display anomalous trends and a variety of mechanisms, but also raise a major problem of structural inheritance. Detailed field investigation and kinematic analysis indicate that the surface ruptures in the Shihkang-Shangchi fault zone are the result of dip-slip thrusting, occasionally with a minor strike-slip component. The surface ruptures emerge at the surface from bedding-parallel thrusts on both limbs of the regional south-plunging syncline. In the middle part of the syncline, bedding-parallel thrusts are connected by thrusts that cross-cut beds. The surface ruptures also reactivate a NE-SW trending anticline (Diaoshenshan), with west-vergent thrust on the backlimb and east-vergent backthrust on the forelimb. This anticline is undergoing uplift by breaking through the regional N-S trending syncline. Combining GPS measurements, seismological data, and geological analyses, we propose a kinematic model with a 3-D fault surface for the 1999 earthquake in the area of the northern termination. We highlight the influence of both the local and regional structures (bedding parallel slip, pre-existing faults and folds) on the development of the earthquake rupture, and hence the role of the structural inheritance. We conclude that the south-plunging regional Pliocene syncline in fact acts as a slip/strain guide for the northern termination of the Chelungpu thrust. The Pliocene Chinshui Shale, as a major source of weakness within the syncline, has strongly influenced the pattern of slip surface during the 1999 earthquake rupture. We interpret the large vertical displacement along the northern segment as the fault rupture occuring over a surface whose radius of curvature tightens toward the north around the core of the syncline.

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