Repeated mechanism of large earthquake-formation mechanism of large scale pseudotachylytes

大尺度拟速岩大地震形成机制的重复机制

基本信息

批准号：
14403009
负责人：
LIN Aiming
金额：
$ 8万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

Main results obtained in this project are as follows.1.Multiple generations of voluminous cataclaiste, mylonite, cataclasite-and mylonite-related pseudotachylytes are found in the Woodroffe thrust, central Australia and ultrahigh pressure metamorphic complex in Diabe-Tonbei region, central China. The co-existence of these fault rocks indicates that the pseudotachylytes represent a large number of large earthquakes and accompanying seismic slip over an extended period of seismicity on these two faults. The timing and distribution of pseudotachylyte shows that the earthquakes nucleated at the base of the brittle-dominated seismogenic zone and propagated down through the brittle-ductile transition into the ductile-dominated regime of the crust.2.Crushing-originated pseudotachylytes are found from the Simotsuburai fault of the Itoigawa-Shizuoka tectonic Line active fault system, central Japan.3.The surface rupture of the 1999 Mw 7.6 Chi-Chi (Taiwan) warthquake was controlled primary by the pre-existing Chenlungpu fault zone, which is distributed in a wide zone of upto 60 m, although the main co-seismic slip is located in a narrow zone of <0.3 cm. The structural analyses of the shear zone and fault rocks found in the Chenlungpu fault show that the Chenlungpu fault has slipped as a thrust fault with a significant left-lateral slip component since its formation in the Pleistocene.4.The magnitude (Ms) 8.1 Central Kunlun earthquake occurred on 14 Novermber 2001, in the central Kunlun mountain area, north Tibet. Our studies reveal 1) that the co-seismic rupturing over a distance of 〜420 km along the pre-existing Kunlun fault zone ; 2) the co-seismic surface rupture was dominated by strike-slip faulting with a large left-lateral displacement up to 16.3 m ; 3) extensive co-seismic mole track structures are developed along the co-seismic rupture zone.

本课题取得的主要成果如下：1.在澳大利亚中部Woodroffe逆冲断层和中国中部Diabe-Tonbei地区超高压变质杂岩中发现了多代大量的碎裂岩、糜棱岩、碎裂岩和糜棱岩相关的假速晶岩。这些断层岩的共存表明，假速岩代表了在一段较长的时间内发生的大量大地震和伴随的地震滑移。这两条断层上的地震活动周期和假速震岩的分布表明，地震在脆性为主的发震带底部成核，并通过脆性-韧性转变向下传播到地壳的韧性为主的区域。2．糸鱼川-静冈构造线活动断层西莫茨布里断层中发现了破碎源假速石3. 1999 年 Mw 7.6 Chi-Chi（台湾）战争地震的地表破裂主要受先存的陈龙堡断裂带控制，该断裂带分布在长达 60 m 的广阔区域，尽管主要-地震滑移位于<0.3 cm的狭窄区域。对陈龙堡断裂中发现的剪切带和断层岩石的结构分析表明，陈龙堡断裂发生了逆冲滑动。 4. 2001 年 11 月 14 日，西藏北部中昆仑山区发生里氏 8.1 级地震。我们的研究表明：1）沿先存昆仑断裂带约420公里的同震破裂；2）同震地表破裂主要是走滑断层活动，左旋位移达16.3 m；3）沿同震破裂带发育广泛的同震痣轨构造。