US-Mexico Planning Visit: Collaborative Study of Active Faulting in Baja California, Mexico

美墨计划访问：墨西哥下加利福尼亚州活动断层合作研究

• 批准号: 1359877
• 负责人: Whitney Behr
• 金额: $ 1.84万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2015-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1359877&HistoricalAwards=false
• 关键词: US; Mexico; Planning; Visit; Collaborative

US-Mexico Planning Visit: Collaborative Study of Active Faulting in Baja California, MexicoProject Summary NSF-CNIC funds will support the initiation of a collaboration between geoscientists at the University of Texas, Austin, and the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE). The long-term research focus of this collaboration will be working toward a better understanding of rates of active faulting and seismic hazard for faults in northern Baja California, which are part of the southern San Andreas Fault system. The primary goal of the initial planning meeting will be to bring together an interdisciplinary team of scientists that will work towards addressing these research goals by first (1) examine existing datasets to highlight critical scientific gaps, (2) compile existing Spanish- and English-language published and unpublished literature, (3) determine how to combine resources to answer key scientific questions and develop new research methods, (4) conduct exploratory field work, and (5) design strategies for disseminating what we learn to local. From a hazard perpective, the collaboration will be focused on the city of Ensenada since it sits above and just north of the Agua Blanca Fault, the largest of two faults in northern Baja California that transfer displacement away from the Pacific-North American tectonic plate boundary that lies to the east. Despite having been recognized as an important structure over half a century ago, because of its location in northwestern Mexico on the periphery of San Andreas system it has garnered little attention. However, recent faulting nearby has served as a reminder that this part of the plate boundary system is too poorly understood given its role in plate boundary deformation. Earthquakes on the Agua Blanca Fault are a primary concern, but the first type of measurements we plan to collect will also help to illuminate its role in transferring slip off shore to other active faults and will lend insight into the proportion of tectonic plate motion that is expressed as earthquake-generating brittle faulting versus more benign diffuse folding.In greater detail, the focus of this project will be to measure new geologic slip rates for the Agua Blanca Fault and by doing so to fill three existing gaps in our understanding of southern San Andreas (sSAF) plate boundary system. First, the new slip rates will inform estimates of the earthquake hazard this fault poses for US and Mexican cities. Existing slip rate estimates for the ABF are highly imprecise, but suggest that it may accommodate as much as 14% of total plate boundary slip. These estimates as well as the geomorphic expression of the ABF are suggestive of a fault that is capable of producing damaging surface ruptures, but the new geologic slip rates are needed to confirm this. Second, new slip rates for the ABF constrain on the amount of plate boundary slip accommodated by the poorly understood network of faults off shore of southern California and northern Baja California. Previous estimates suggest a 2-20% of total plate boundary slip may be accommodated off shore, but confirming this by collecting sub-marine slip rates is complex and expensive. However, since the ABF is the primary fault feeding slip offshore, its slip rate constrains the minimum offshore slip rate. Third, new ABF slip rates will help to reveal the proportion of plate boundary slip that is absorbed by off-fault distributed deformation rather than brittle faulting. Geodetic and geologic slip rates indicate that the major onshore faults in this region accommodate roughly 80% of total relative plate motion. Since the new ABF slip rates will constrain how much plate boundary slip is accommodated off shore, whatever remains of the 20% slip deficit after both on- and offshore slip is accounted for can be attributed to undetected off-fault distributed deformation. In these ways, this we hope to harness the strengths of multiple scientists from universities in both the US and Mexico to answer key outstanding questions regarding seismic hazard and slip partitioning in a prominent but poorly understood section of the southern San Andreas Fault system.

美国墨西哥计划访问：墨西哥摘要NSF-CNIC FUNDS在加利福尼亚州Baja加利福尼亚的积极故障的合作研究将支持德克萨斯大学，奥斯汀大学和Centro de InvestiondevistionAciónSuperior de Ensenada（Cicese）的地球科学家之间合作的倡议。这项合作的长期研究重点将致力于更好地理解积极的断层和地震危险的危害，这是南巴哈北加利福尼亚州的断层，这是南部圣安德烈亚斯南部断层系统的一部分。 The primary goal of the initial planning meeting will be to bring together an interdisciplinary team of scientists that will work towards addressing these research goals by first (1) examining existing datasets to highlight critical scientific gaps, (2) compile existing Spanish- and English-language published and unpublished literature, (3) determine how to Combine resources to answer key scientific questions and develop new research methods, (4) conduct exploratory field work, and (5) design strategies for disseminating我们学到了当地的东西。从危险的角度来看，该合作将集中在恩塞纳达市，因为它位于Agua Blanca断层的上方和北部，这是加利福尼亚州北巴哈北部两个断层中最大的断层，这些断层从位于东部的太平洋北美构造板块边界上转移。尽管在半个世纪前被公认为是一个重要的结构，但由于它在墨西哥西北部的圣安德烈亚斯系统外围的位置，但它几乎没有引起关注。然而，最近的近乎断层的提醒是，板边界系统的这一部分对其在板边界变形中的作用太糟糕了。 Agua Blanca断层上的地震是主要问题，但是我们计划收集的第一类测量类型也将有助于阐明其在将岸边滑落到其他主动故障中的作用，并将深入了解构造板块运动的比例，该构造板运动的比例表示为地震生成较大的差异，以衡量较大的差异，这将是对较大的差异的范围。 Blanca断层，并在我们对南部圣安德烈亚斯（SSAF）板块边界系统的理解中填补三个现有空白。首先，新的滑移率将为我们和墨西哥城市所构成的地震危害估计。 ABF的现有滑移速率估计值高度可靠，但建议它可以容纳多达总板边界滑移的14％。这些估计值以及ABF的地貌表达表明了能够产生破坏性表面破裂的断层，但是需要新的地质滑动速率来确认这一点。其次，ABF限制的新滑动率对板界滑移量的数量限制了，该板边界滑移量较低，而南加州和北加州北部的岸上的断层网络所容纳了。先前的估计表明，可以容纳板块总板边界滑移的2-20％，但通过收集亚航线滑动速率来确认这一点是复杂且昂贵的。但是，由于ABF是离岸的主要断层馈电滑动滑移，因此其滑动率限制了最小离岸滑移速率。第三，新的ABF滑动速率将有助于揭示板边界滑移的比例，而板边界滑移的比例被OFFEART分布式变形而不是脆性断层所吸收。地质和地质滑移速率表明该区域的主要陆上断层约为总相对板运动的80％。由于新的ABF滑动速率将限制在岸上容纳多少板边界滑移，因此在陆上和离岸滑移后的20％滑移赤字中剩下的任何东西都可以归因于未发现的off损坏分布式变形。通过这些方式，我们希望利用美国和墨西哥大学的多个科学家的优势，以在南部圣安德烈亚斯断层系统的一个突出但不理解的部分中回答有关地震危害和滑动分区的关键问题。