Collaborative Research: Postseismic deformation for the Izmit-Duzce, Turkey earthquakes: Implications for the mechanics of the earthquake cycle and rheology of the continent

合作研究：土耳其伊兹米特-迪兹杰地震的震后变形：对地震周期力学和大陆流变学的影响

• 批准号: 1045487
• 负责人: Robert Reilinger
• 金额: $ 6.5万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2012-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045487&HistoricalAwards=false
• 关键词: Collaborative; Research; Postseismic; deformation; Izmit

The 1999 Izmit, Turkey earthquake sequence (M=7.5, August, Gulcuk and M=7.1, November, Duzce earthquakes) occurred within a pre-existing GPS network making it one of the most geodetically well observed seismic events on a major continental strike slip fault. Well-defined pre-earthquake strain accumulation, coseismic motions (reaching ~2 m), short-term (days - months) postseismic afterslip, and longer-term (years - 10 years) postseismic relaxation are all well imaged by geodetic observations. In addition, the earthquake appears to have altered the character of interseismic motions in unexpected ways (i.e., not easily ascribed to standard postseismic processes) as far as 200 - 300 km from the coseismic fault. As such, this event is providing fundamental constraints on the earthquake deformation cycle (inter-, pre-, co-, and postseismic) with direct implications for forecasting future earthquakes on this fault system, and by analogy for understanding the dynamics of similar strike slip faults, including the San Andreas Fault in California.The 1999 sequence occurred along the eastern segment of a seismic gap that extends south of Istanbul across the Sea of Marmara, raising serious concerns about a future earthquake on the western Marmara segment that could have devastating effects on this vulnerable mega-city ( 20 million people). Uncertainty persists about the possible magnitude of future earthquakes in the Marmara Sea, as well as how strain is transferred from the Izmit segment to the Main Marmara Fault (MMF) within the Sea (i.e., the geometry, degree of locking, slip rate on the connecting fault). The Princes Islands are located within the Marmara south of Istanbul and approach within less than 5 km of the Izmit-Marmara connecting fault segment. Two islands (Sivriada and Büyükada) located very near the connecting segment have been selected for ICDP borehole sites (GFZ, Germany are leading this ICDP initiative). In cooperation with this work, we are focusing our initial efforts on installing GPS stations at both borehole sites. Data from these stations will be downloaded by our Turkish partners at the Marmara Research Center and by UNAVCO. Over three years, these GPS observations will provide improved constraints on the dip, locking depth, and present-day rate of strain accumulation on this fault segment. These anticipated results together with analyses of postseismic deformation throughout the Marmara region, promise to provide improved understanding of the earthquake deformation cycle, and accordingly, estimates of the timing and magnitude of future earthquakes in the Sea of Marmara.This project is funded by the Geophysics and Tectonics Programs of NSF.

1999 年土耳其伊兹米特地震序列（古尔丘克 8 月 7.5 级地震和迪兹杰 11 月 7.1 级地震）发生在预先存在的 GPS 网络内，使其成为主要大陆走滑断层上大地测量学上观测最清楚的地震事件之一。 明确的震前应变积累、同震运动（达到~2 m）、短期（数天至数月）震后余滑以及长期（数年至10年）震后弛豫都可以通过大地测量得到很好的成像。 此外，距同震断层 200 - 300 公里的地震似乎以意想不到的方式改变了震间运动的特征（即不易归因于标准震后过程）。 因此，这一事件为地震变形周期（震间、震前、同震和震后）提供了基本约束，对预测该断层系统未来的地震有直接影响，并通过类比了解类似走滑断层（包括加利福尼亚州圣安德烈亚斯断层）的动态。1999年的序列发生在地震间隙的东段，该地震间隙从伊斯坦布尔以南延伸到地中海。 马尔马拉，人们对马尔马拉西部地区未来发生的地震表示严重担忧，地震可能会对这座脆弱的大城市（2000 万人口）造成毁灭性影响。 马尔马拉海未来可能发生的地震震级以及应变如何从伊兹米特段转移到海内马尔马拉主断层（MMF）（即连接断层的几何结构、锁定程度、滑动率）仍然存在不确定性。王子群岛位于伊斯坦布尔以南的马尔马拉河内，距离伊兹米特-马尔马拉连接断层段不到 5 公里。 位于非常靠近连接段的两个岛屿（Sivriada 和 Büyükada）已被选为 ICDP 钻孔地点（德国 GFZ 领导了该 ICDP 计划）。 为了配合这项工作，我们最初的工作重点是在两个钻孔地点安装 GPS 站。 这些站的数据将由我们在马尔马拉研究中心的土耳其合作伙伴和 UNAVCO 下载。三年内，这些 GPS 观测结果将对该断层段的倾角、锁定深度和当前应变累积率提供改进的约束。 这些预期结果加上对整个马尔马拉地区震后变形的分析，有望加深对地震变形周期的了解，从而估计马尔马拉海未来地震的时间和震级。该项目由美国国家科学基金会地球物理学和构造学计划资助。