The 1999 Izmit earthquake sequence in turkey:: Seismological and tectonic aspects
The 1999 Izmit earthquake sequence in turkey:: Seismological and tectonic aspects
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DOI：
10.1785/0120000838
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发表时间：
2002-02-01
影响因子：
3
通讯作者：
Yörtük, A
中科院分区：
文献类型：
--
作者：
Özalaybey, S;Ergin, M;Yörtük, A
伊兹米特/杜兹采地震序列是土耳其地震史上现代数字台网记录到的最大地震序列。（M-w 7.4）伊兹米特主震发生在1999年8月17日00时01分38.7秒（UTC），东经29.967度，北纬40.729度，深度13公里，之前至少发生了8次震级M-L < 3.0的直接前震。余震位置显示，一个大的地区已成为地震非常活跃的主震后，大部分的余震区迅速发展的头3天。余震的分布阐明了与余震区北安纳托利亚断层（NAF）的各个分支有关的许多地震构造。地震活动模式定义了一个破裂面，延伸约80公里的东和75公里的主震震中，确认主震期间的双边破裂。西部余震活动几乎全部位于近海，沿着伊兹米特湾轴线延伸。我们发现，最西端的主震破裂达到了近海地区，仅10公里以南的王子群岛。走滑运动的优势是伊兹米特层序的主要特征之一。一些重要的余震群发生在推断的主震破裂面之外。这些集群的空间和时间发生表明，它们是由复杂的应力和动态应变的再分布所施加的主震位错触发。位于破裂带西端的地震的震源机制表现为走滑和正断层两种机制。我们推断亚洛瓦星系团是由主震触发的。正常的断层机制的优势支持的概念，动态拉伸应变在触发这个集群中发挥了重要作用。位于王子群岛的四个事件表明类似的震源机制，其特征是平行于北方边界断层（NBF）走向的右行走滑运动和余震分布的局部趋势。这一观察导致一阶地震构造证据的性质的NBF，这是已知的是一个transtensional功能在表面上，是占主导地位的走滑运动在深度。马尔马拉海的走滑和伸展地震构造特征的共存突出了应变分配的重要性，浅transstentional结构，容纳南北延伸和更深的结构与NAF容纳东西右行剪切。
The Izmit/Duzce earthquake sequence is the largest sequence recorded by modem digital networks in the history of Turkish earthquakes. The (M-w 7.4) Izmit mainshock occurred at 29.967degrees E and 40.729degrees N, and 13 km depth at 00 hr 0 1 min 38.7 sec UTC, on 17 August 1999 and was preceded by at least eight immediate foreshocks of magnitude M-L < 3.0. Aftershock locations show that a large region has become seismically very energetic following the mainshock and that most of the aftershock zone developed quickly in the first 3 days. The distribution of the aftershocks illuminates numerous seismotectonic structures associated with the various branches of the North Anatolian Fault (NAF) in the aftershock zone. The seismicity pattern defines a rupture plane that extends about 80 kin east and 75 km west of the mainshock epicenter, confirming bilateral rupture during the mainshock. The western aftershock activity is almost entirely located offshore, extending along the axis of the Izmit Bay. We show that the westernmost extent of the mainshock rupture reached the offshore region, just 10 km south of the Princes Islands. The dominance of strike-slip motion is one of the main characteristics of the Izmit sequence. A number of significant aftershock clusters occur off the inferred mainshock rupture plane. The spatial and temporal occurrence of these clusters show that they are triggered by the complex redistribution of stresses and dynamic strains imposed by the dislocation of the mainshock. The focal mechanisms of the events located in the western end of the rupture zone show both strike-slip and normal-faulting mechanisms. We infer that the Yalova cluster was triggered by the mainshock. The dominance of the normal faulting mechanisms supports the notion that dynamic extensional strains played a major role in triggering this cluster. Four events located off the Princes Islands indicate similar source mechanisms characterized by right-lateral strike-slip motion parallel to the strike of the Northern Boundary Fault (NBF) and local trend of aftershock distribution. This observation leads to a first order seismotectonic evidence that the nature of the NBF, which is known to be a transtensional feature at the surface, is dominated by strike-slip motion at depth. The coexistence of strike slip and extensional seismotectonic features in the Sea of Marmara highlights the importance of strain partitioning amongst shallow transtentional structures accommodating north-south extension and deeper structures associated with the NAF accommodating east-west right-lateral shear.