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首页> 外文期刊>Tectonophysics: International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth >Determination of three-dimensional in situ stresses by anelastic strain recovery in Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1)
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Determination of three-dimensional in situ stresses by anelastic strain recovery in Wenchuan Earthquake Fault Scientific Drilling Project Hole-1 (WFSD-1)

机译：通过弹性应变恢复确定汶川地震断层科学钻探工程Hole-1（WFSD-1）的三维原地应力

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摘要

The Wenchuan Earthquake Fault Scientific Drilling Projectwas implemented rapidly after the great 12 May 2008 earthquake (Mw 7.9) to better understand rupture mechanisms of the seismic faults. The first borehole of the project, WFSD-1 was located in Hongkou Township, Dujiangyan City, Sichuan Province, China on the hanging wall of the Yingxiu–Beichuan fault, which underwent large dextral and vertical displacement during the earthquake. The near-vertical boreholewas 1201 mlong. In-situ stresseswere measured in rock samples fromdepths between 424 and 1173 m drilling depth by the anelastic strain recovery (ASR) method. The average trend of the maximumprincipal stress σ_1 was N309° (ranging from N291° to N325°), rotatedwith increasing borehole depth fromNW–SE to WNW–ESE. Themagnitude of the in-situ maximumprincipal stresswas estimated to be 35.3 MPa at the depth of 1173 m. The relations between horizontal and vertical stresses are vertical stress σ_v > maximum horizontal stress σ_H > minimumhorizontal stress σh at depths above 424 m, σ_H > σ_h > σ_v at depths from 424 m to 800 m, and σ_H > σ_v > σ_h belowthe depth of 800 m. These indicate that the stress states are in a normal faulting stress regime above 424 m; a reverse faulting regime from 424 mto 800 mand a dextral strike-slip regime below 800 m. The stress measurements from WFSD-1 are consistent with the focal mechanism solution in which the mainshock was dominated by thrusting accompanied by dextral strike-slip motion. The orientations of σ_1 are roughly consistent with the tectonic displacement direction of the Longmenshan area, which provides further evidence of NW–SE movements representing compression of the Songpan–Ganzi block toward the Sichuan basin.
机译：汶川地震断层科学钻探项目在2008年5月12日大地震（7.9兆瓦）之后迅速实施，以更好地了解地震断层的破裂机制。该项目的第一个钻孔WFSD-1位于中国四川省都江堰市虹口镇，位于映秀-北川断层的悬壁上，地震期间发生了较大的右旋和竖向位移。近垂直井眼长1201米。通过非弹性应变恢复（ASR）方法在424至1173 m的钻探深度处测量了岩石样品的原位应力。最大主应力σ_1的平均趋势为N309°（从N291°到N325°），并且随着井眼深度从NW–SE到WNW–ESE的增加而旋转。在1173 m的深度处，原位最大主应力的大小估计为35.3 MPa。水平应力和垂直应力之间的关系是在424 m以上的深度处的垂直应力σ_v>最大水平应力σ_H>最小水平应力σh，在424 m至800 m的深度处σ_H>σ_h>σ_v和在800深度以下σ_H>σ_v>σ_h米这些表明应力状态在424 m以上处于正常断层应力状态。从424 m到800的反向断层状态，要求在800 m以下的右旋走滑状态。 WFSD-1的应力测量结果与震源机制解决方案一致，在该震源机制解决方案中，主震主要由推力伴有右旋走滑运动控制。 σ_1的方向大致与龙门山地区的构造位移方向一致，这进一步提供了西北—东南运动代表松潘—甘孜地块向四川盆地压缩的证据。

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