喀什—乌恰地区近年来强震活动平静的可能成因
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摘要
通过分析喀什—乌恰地区和伽师—柯坪块区强震产生的静态库仑破裂应力变化(ΔCFS),从断层相互作用和中等地震活动加、减速特征的角度,初步论证了两个区域强震活动交替发生特征的可能机理。库仑破裂应力和加速矩释放模型拟合结果表明,伽师—柯坪地区1997—1998年成组发生的伽师6级强震、新疆南部周边发生的1992年苏萨梅尔MS7.5地震和2005年巴基斯坦7.8级地震产生的静态应力变化不利于喀什—乌恰地区强震的发生,可能使得该区后续强震的发生时间延迟了。另一方面,位于1992年苏萨梅尔MS7.5地震和1997—2003年伽师系列强震产生的ΔCFS为负的喀什—乌恰地区地震活动表现为弱加速特征,这或许是1993年以来喀什—乌恰地区强震平静特征的原因。喀什—乌恰地区7级地震产生的正的ΔCFS可能有利于伽师—柯坪地区后续强震的发生,3组7级地震产生的ΔCFS为正的区域内后续强震发生前均出现了一定程度的加速特征,从而定量解释了喀什—乌恰地区强震活动对伽师—柯坪块区地震活动的影响。
By analyzing static Coulomb failure stress change(ΔCFS) from strong earthquakes in Kashi-Wuqia region and Jiashi-Keping block,and combining with fault interaction and the accelerated and decelerated characteristics of moderate earthquakes,the article analyzes the possible mechanism of alternant occurrence of strong earthquakes in the two regions.Coulomb failure stress change and fitting result of accelerated moment release model show that 1997 to 1998 grouped Jiashi strong earthquakes with MS6 in Jiashi-Keping region,1992 Susamer earthquake with MS7.5 occurred in the southern Xinjiang and 2005 Pakistan earthquake with MS7.8 discourage the occurrence of strong earthquakes in Kashi-Wuqia region,and maybe delay the occurrence of the following strong earthquakes. On the other hand,seismic activity in the Kashi-Wuqia region with the negative ΔCFS,where is from 1992 Susamer earthquake with MS7.5 and 1997 to 2003 Jiashi strong earthquakes,is characteristics of weak acceleration,which possibly results in the quiescence of strong earthquakes from 1993 in Kashi-Wuqia region.The positive ΔCFS from MS7 earthquakes in Kashi-Wuqia region maybe encourages the following strong earthquakes in Jiashi-Keping region,and there exists certain accelerated characteristics before the following strong earthquakes in the positive ΔCFS region from 3 grouped MS7 earthquakes,which explains quantitatively the influence of strong earthquake activity in Kashi-Wuqia region on seismicity in Jiashi-Keping region.
By analyzing static Coulomb failure stress change(ΔCFS) from strong earthquakes in Kashi-Wuqia region and Jiashi-Keping block,and combining with fault interaction and the accelerated and decelerated characteristics of moderate earthquakes,the article analyzes the possible mechanism of alternant occurrence of strong earthquakes in the two regions.Coulomb failure stress change and fitting result of accelerated moment release model show that 1997 to 1998 grouped Jiashi strong earthquakes with MS6 in Jiashi-Keping region,1992 Susamer earthquake with MS7.5 occurred in the southern Xinjiang and 2005 Pakistan earthquake with MS7.8 discourage the occurrence of strong earthquakes in Kashi-Wuqia region,and maybe delay the occurrence of the following strong earthquakes. On the other hand,seismic activity in the Kashi-Wuqia region with the negative ΔCFS,where is from 1992 Susamer earthquake with MS7.5 and 1997 to 2003 Jiashi strong earthquakes,is characteristics of weak acceleration,which possibly results in the quiescence of strong earthquakes from 1993 in Kashi-Wuqia region.The positive ΔCFS from MS7 earthquakes in Kashi-Wuqia region maybe encourages the following strong earthquakes in Jiashi-Keping region,and there exists certain accelerated characteristics before the following strong earthquakes in the positive ΔCFS region from 3 grouped MS7 earthquakes,which explains quantitatively the influence of strong earthquake activity in Kashi-Wuqia region on seismicity in Jiashi-Keping region.
引文
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[11]Simpson R W,Reasenberg P A.Earthquake-induced Static Stress Changes on central Californiafaults[A].In:Simpson R W eds.The Loma Prieta.California Earthquake of October 17.1989-Tectonic processes and models[C].US Geol Surv Prof.Pap.1994,55-89.
[12]Bufe C G,Varnes D J.Predictive modeling of the seismic cycle of the greater San Francisco Bay Re-gion[J].J Geophys Res,1993,98:9 871-9 883.
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①《新疆巴楚—伽师6.8级地震及未来强震趋势研究》报告,2005。
[2]Reasenberg P A,Simpson R W.Response of regional seismicity to the static stress change producedby the Loma Prieta earthquake[J].Science,1992,255:1 687-1 690.
[3]万永革,吴忠良,周公威,等.地震静态应力触发模型的全球检验[J].地震学报,2002,24(3):302-316.
[4]Jaume S C,Sykes L R.Evolving towards a critical point:a review of accelerating seismic moment/energy release prior to large and great earthquake[J].Pure App1 Geophys,1999,155:279-306.
[5]Bowman D D,G King C P.Accelerating seismicity and stress accumulation before large earthquakes[J].Geophys Res Lett,2001,28:4 039-4 042.
[6]马禾青,赵卫明,张文孝,等.地震活动加速模型在西北地区的应用[J].西北地震学报,2003,25(4):344-347.
[7]蒋长胜,吴忠良,史勇军.中强震前地震活动矩释放加速现象(AMR)的普遍性问题[J].中国地震,2004,20(2):119-125.
[8]周仕勇,许忠淮,陈晓非.伽师强震群震源特征及震源机制力学成因分析[J].地球物理学报,2001,44(5):654-662.
[9]郝平,田勤俭,傅征祥,等.2000年1月15日姚安6.5级地震较强余震的应力触发[J].地震研究,2004,27(3):246-251.
[10]Okada Y.Internal deformation due to shear and tensile faults in a half-space[J].Bull Seism Soc A-mer,1992,82:1 018-1 040.
[11]Simpson R W,Reasenberg P A.Earthquake-induced Static Stress Changes on central Californiafaults[A].In:Simpson R W eds.The Loma Prieta.California Earthquake of October 17.1989-Tectonic processes and models[C].US Geol Surv Prof.Pap.1994,55-89.
[12]Bufe C G,Varnes D J.Predictive modeling of the seismic cycle of the greater San Francisco Bay Re-gion[J].J Geophys Res,1993,98:9 871-9 883.
[13]王筱荣.柯坪块体的地震活动特征[J].西北地震学报,2001,23(4):382-388.
①《新疆巴楚—伽师6.8级地震及未来强震趋势研究》报告,2005。
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