New constraints on micro-seismicity and stress state in the western part of the North Anatolian Fault Zone: Observations from a dense seismic array
New constraints on micro-seismicity and stress state in the western part of the North Anatolian Fault Zone: Observations from a dense seismic array
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DOI：
10.1016/j.tecto.2015.06.022
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发表时间：
2015-08
期刊：
影响因子：
2.9
通讯作者：
S. Altuncu Poyraz;M. U. Teoman;N. Türkelli;M. Kahraman;D. Cambaz;A. K. Mutlu;S. Rost;G. Houseman;David Thompson;D. Cornwell;M. Utkucu;L. Gülen
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文献类型：
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作者：
S. Altuncu Poyraz;M. U. Teoman;N. Türkelli;M. Kahraman;D. Cambaz;A. K. Mutlu;S. Rost;G. Houseman;David Thompson;D. Cornwell;M. Utkucu;L. Gülen
为了广泛调查北安纳托利亚断裂带西段下方的地壳结构，该断裂带分为南北两支，2012年5月初在萨卡里亚地区部署了一个由70个台站组成的临时地震台网(北安纳托利亚-达纳密集台阵)，并在FaultLab实验期间运行了18个月。在2437个受爆炸污染的事件中，我们提取了1371个位置良好的地震。扩大的台站覆盖范围具有7公里的名义台站间距，从而导致最小震级计算为0.1级。阵列内的水平和垂直位置不确定度分别不超过0.8公里和0.9公里。我们在断层的两个分支上观测到了相当大的地震活动，那里的孕震带深度大多被限制在15公里以内。利用我们目前的地震目录，我们得到了b值为1。我们还绘制了b值随深度的变化图，并观察到b值逐渐减少。在此基础上，用P波初动极化法确定了41个1.8级以上地震的震源参数。区域矩张量反演法也被应用于3.0级以上地震。震源机制解证实了Sakarya及其邻区受到以斜滑运动为主的挤压体制的应力作用。应力张量分析表明，最大主应力沿WNW-ESE方向排列，张力轴沿NNE-SSW方向排列。(C)2015爱思唯尔B.V.保留所有权利。
With the aim of extensively investigating the crustal structure beneath the western segment of the North Anatolian Fault Zone where it splays into northern and southern branches, a temporary seismic network (dense array for North Anatolia-DANA) consisting of 70 stations was deployed in early May 2012 and operated for 18 months in the Sakarya region during the FaultLab experiment. Out of 2437 events contaminated by explosions, we extracted 1371 well located earthquakes. The enhanced station coverage having a nominal station spacing of 7 km, lead to a minimum magnitude calculation of 0.1. Horizontal and vertical location uncertainties within the array do not exceed 0.8 km and 0.9 km, respectively. We observe considerable seismic activity along both branches of the fault where the depth of the seismogenic zone was mostly confined to 15 km. Using our current earthquake catalog we obtained a b-value of 1. We also mapped the b-value variation with depth and observed a gradual decrease. Furthermore, we determined the source parameters of 41 earthquakes with magnitudes greater than 1.8 using P-wave first motion polarity method. Regional Moment Tensor Inversion method was also applied to earthquakes with magnitudes greater than 3.0. Focal mechanism solutions confirm that Sakarya and its vicinity is stressed by a compressional regime showing a primarily oblique-slip motion character. Stress tensor analysis indicates that the maximum principal stress is aligned in WNW-ESE direction and the tensional axis is aligned in NNE-SSW direction. (C) 2015 Elsevier B.V. All rights reserved.