Collaborative Research: Stratigraphic, Geomorphic, and Paleoseismologic Record of Coseismic Fold Growth in Western Argentina

合作研究：阿根廷西部同震褶皱生长的地层、地貌和古地震记录

• 批准号: 0409443
• 负责人: Andrew Meigs
• 金额: $ 15.6万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409443&HistoricalAwards=false
• 关键词: Collaborative; Research; Stratigraphic; Geomorphic; Paleoseismologic

Thrust faults are a major seismic hazard worldwide. Seismic hazard assessment for thrust faults depends on understanding the timing, frequency, and size of past earthquakes. Thrust fault earthquakes are often accompanied by folding in the shallow subsurface. Folds are the cumulative product of repeated earthquakes. Thus, knowledge of how much, with what frequency, and with what geometry folds grow in individual earthquakes is essential for determining how fold growth relates to earthquake size on thrust faults. In two areas in western Argentina, growth strata and geomorphic surfaces contain information about folding and represent two repositories of the earthquake history of the associated thrust faults. Structural, geomorphic, and paleoseismologic study of the two areas is revealing a detailed record of coseismic and long-term deformation and providing new insight into the geomorphic and stratigraphic signature of folding on earthquake timescales. A field-calibrated model of the production of geomorphic surfaces or growth strata in an individual thrust earthquake is being developed based on the surface effects of a large and damaging earthquake in 1944. Moreover, the new data are contributing directly to the Argentinean national seismic hazard assessment program. The cities of Mendoza and San Juan have a combined population of more than 1.5 million people and are located near active earthquake faults with little constraints on their past activity or future potential for earthquakes. This study is providing a template for the recognition of paleoearthquakes from folds and a new method of thrust earthquake hazard recognition. This project is being supported by the Geosciences Directorate and the Office of International Science and Engineering.

逆冲断层是世界范围内的一大地震灾害。逆冲断层的地震危险性评估取决于对过去地震的时间、频率和规模的了解。逆冲断层地震往往伴随着浅层地下的褶皱。褶皱是反复地震的累积产物。因此，了解个别地震中褶皱的增长程度、频率和几何形状，对于确定褶皱增长与逆冲断层上的地震规模之间的关系至关重要。在阿根廷西部的两个地区，生长层和地貌面包含有关褶皱的信息，代表了相关逆冲断层的地震历史的两个储存库。这两个地区的构造、地貌和古地震学研究揭示了同震和长期变形的详细记录，并为了解地震时间尺度上褶皱的地貌和地层特征提供了新的见解。根据1944年一次破坏性大地震的地表效应，正在开发一种在个别逆冲地震中产生地貌面或生长层的现场校准模型。此外，这些新数据还直接为阿根廷国家地震危险性评估项目做出了贡献。门多萨和圣胡安两个城市的总人口超过150万，位于地震活动断层附近，对它们过去的活动或未来发生地震的可能性几乎没有限制。本研究为从褶皱中识别古地震提供了模板，为逆冲地震危险性识别提供了一种新的方法。该项目得到了地球科学局和国际科学与工程办公室的支持。