Geodetic observations of postseismic creep in the decade after the 1999 Izmit earthquake, Turkey: Implications for a shallow slip deficit
Geodetic observations of postseismic creep in the decade after the 1999 Izmit earthquake, Turkey: Implications for a shallow slip deficit
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DOI：
10.1002/2015jb012737
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发表时间：
2016-04-01
影响因子：
3.9
通讯作者：
Houseman, Gregory A.
中科院分区：
文献类型：
--
作者：
Hussain, Ekbal;Wright, Tim J.;Houseman, Gregory A.
地震滑动和构造荷载之间的关系对于理解沿断层的应变积累模式及其产生大地震的能力都是重要的。利用Envisat干涉合成孔径雷达（InSAR）数据的时间序列分析，研究了1999年伊兹米特（Izmit）和杜兹塞（Duzce）地震断裂的全部范围和2002-2010年的地震蠕变的空间分布和时间演变。横过断层的视线速度的不连续性意味着断层蠕变以断层平行的平均速度到达地球表面，沿着NAF大约80公里的路段，速度大约为5毫米/年。通过结合InSAR和公布的GPS速度，我们能够提取运动的垂直和东西分量，并表明Adapazari盆地正在以类似于6毫米/年的速度下沉。垂直运动对该地区以前的蠕变估计有偏差。断层附近的位移时间序列与基于速率-状态摩擦的余震模型一致，该模型预测了伊兹米特地震后断层蠕变速率在5年后迅速减速至接近5 mm/yr的稳定状态。将我们的模型预测到未来200年，我们发现1-1.3 m的累积位移不足以解释以前研究中观察到的浅层同震滑动亏损。在地震周期中，可能需要浅层地壳中分布的断层外变形或瞬态快速滑动来释放一些长期应变。
The relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes. We investigate the spatial distribution and temporal evolution of aseismic creep on the western North Anatolian Fault (NAF) using time series analysis of Envisat interferometric synthetic aperture radar (InSAR) data, covering the full extent of the 1999 Izmit and Duzce earthquake ruptures and spaming 2002-2010. Discontinuities in the line-of-sight velocity across the fault imply that fault creep reaches the Earth's surface at an average fault-parallel rate of similar to 5 mm/yr along an similar to 80 km section of the NAF. By combining InSAR and published GPS velocities, we are able to extract the vertical and east-west components of motion and show that the Adapazari basin is subsiding at a rate of similar to 6 mm/yr. Vertical motions have biased previous estimates of creep in this region. The displacement time series close to the fault is consistent with an afterslip model based on rate-and-state friction, which predicts a rapid deceleration in fault creep rate after the Izmit earthquake to a near-steady state similar to 5 mm/yr after 5 years. Projecting our model 200 years into the future we find that the cumulative displacement of 1-1.3 m is insufficient to account for the shallow coseismic slip deficit observed in previous studies. Distributed off-fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long-term strain during the earthquake cycle.