Collaborative Proposal: Postseismic deformation of the Izmit-Duzce, Turkey earthquake sequence: implications for the mechanics of the earthquake cycle and rheology of the continent

Izmit-Duzce地震序列(M=7.4，17/08/1999；M=7.2，12/11/1999)提供了一个独特的机会来回答有关地震周期的性质(应变累积和释放机制)以及地壳和上地幔的流变性等长期存在的基本问题。我们正在为这些地震开发的大地测量数据集既包括地震断层周围确定的震前速度场，也包括同震形变带(近场和远场)内的GPS站网络，该网络捕获了初始、快速和持续的较长期震后变形。这是世界上最完整的大陆大地震形变的大地测量记录之一。在地震序列之前、期间和之后进行的详细地震观测，断层偏移量的现场测绘，卫星图像(SPOT)和大地测量(InSAR)研究，以及沿北安纳托利亚断层(NAF)从东到西传播的20世纪地震序列的地质研究，几乎使该断层全长1200公里(不包括马尔马拉段)破裂，有助于解释大地测量记录。此外，NAF拥有长达2000年、记录良好的历史地震记录，与受良好约束的古地震记录和最近的大地测量观测一起，为检验大陆断裂的地震模型提供了广泛的数据集。与我们的土耳其合作伙伴合作，我们建议使用广泛的可用GPS和InSAR数据目录来限制Izmit-Duzce地震序列之后的持续变形，并扩展我们的建模工作，以产生对NAF系统地震周期动态的定量描述。这项拟议的研究建立在我们先前工作(Ergintav等人，2009年；HearNet等人，2009)的基础上，其中包括分析6.5年的震后GPS观测(包括连续的[CGPS]和[SGPS])，以表征初始和早期震后运动的时间和空间行为，以及对地震序列后最初的2.5年期间进行动态模拟。此外，最近的InSAR分析(Cakir等人，2012年)为震后变形提供了一个重要的新约束条件，该分析要求重新评估地震后后期沿地震断层大段的余滑的作用，这可能会对地震危险产生重大影响。拟议的研究将提供一套关于大陆主要走滑断层的地震周期性质的重要观察，对地震力学有直接影响，估计地震重复次数，作为应力状态的函数的地壳和上地幔流变性，以及地震过程和区域构造之间的相互作用。这一案例研究提供了关于大陆走滑断层的一般机制的信息，包括圣安德烈亚斯断层、大伊斯坦布尔地区的地震和海啸灾害以及国际科学合作的机会。

The Izmit-Duzce earthquake sequence (M=7.4, 17/08/1999; M=7.2, 12/11/1999) offers a uniqueopportunity to answer long-standing, fundamental questions about the nature of the earthquake cycle(mechanics of strain accumulation and release), and the rheology of the crust and upper mantle. Thegeodetic data set we are developing for these earthquakes includes both a well-determined preearthquakevelocity field around the earthquake fault, and a network of GPS stations within the coseismicdeformation zone (near and far field) that captured the initial, rapid, and ongoing longer-termpostseismic deformation. This is one of the most complete geodetic records of deformation for any majorcontinental earthquake anywhere in the world.Interpretation of the geodetic record is facilitated by detailed seismic observations before, during,and following the earthquake sequence, field mapping of fault offsets, satellite image (SPOT) andgeodetic (InSAR) studies, and geologic studies of the 20th Century sequence of earthquakes thatpropagated along the North Anatolian Fault (NAF) from E to W fracturing almost the full 1200 km lengthof the fault (excluding the Marmara segment). Furthermore, the NAF has a long and well recordedhistorical seismic record extending back almost 2000 years that, along with the well-constrainedpaleoseismic record and recent geodetic observations, provides an extensive data set for testingearthquake models of continental faulting.In collaboration with our Turkish partners, we propose to use an extensive catalogue of availableGPS and InSAR data to constrain continuing deformation following the Izmit-Duzce earthquakesequence, and to extend our modeling effort to produce a quantitative description of the dynamics of theNAF system seismic cycle. The proposed research builds on our prior efforts (Ergintav et al., 2009; Hearnet al., 2009) that included analysis of 6.5 years of postseismic GPS observations (both continuous [CGPS]and survey [SGPS]) to characterize the temporal and spatial behavior of initial, and early postseismicmotions, and dynamic modeling for the initial 2.5-year period following the earthquake sequence. Inaddition, an important new constraint on postseismic deformation is provided by recent InSAR analysis(Cakir et al., 2012) that requires a re-evaluation of the role of afterslip along a substantial segment of thecoseismic fault late in the postseismic period, potentially with major implications for seismic hazards.The proposed research will provide an important set of observations on the natureof the earthquake cycle for a major continental strike-slip fault with direct implications for earthquakemechanics, estimating earthquake repeat times, crust and upper mantle rheology as a function of the stateof stress, and interaction between earthquake processes and regional tectonics. This case study provides information on the mechanics of continental strike-slip faults in general, including the San Andreas Fault, earthquake and tsunami hazards in the greater Istanbul area, and opportunities for international scientific collaboration.