RUI: Investigating Disagreements Between Geologically and Geodetically Estimated Slip Rates for the San Bernardino and San Gorgonio Pass Sections of the San Andreas Fault

调查圣安德烈亚斯断层的圣贝纳迪诺和圣戈戈尼奥山口段的地质和大地测量估计的滑动速率之间的分歧。该奖项支持旨在更好地了解圣安德烈亚斯断层南部滑动速度的工作，该地区在不同的时间间隔报告了高度不协调的滑动速度。圣安德烈亚斯断裂圣贝纳迪诺段的全新世或最新更新世滑动速率(15-25毫米/年)比基于弹性大地测量数据的滑动速率(一般小于或等于5毫米/年)大3-5倍。这是目前应变累积速率与全新世至最新更新世应变释放速率之间已知的最大差异之一。这一差异是否表明这段断层不再像以前那样活跃？或者，这是整个地震周期内应变累积速率不均匀的结果？沿着这段断层的东北侧，圣贝纳迪诺山脉的大地测量数据很稀少。因此，在这些关于速率差异原因的问题完全得到解决之前，重要的是要知道，明显较低的大地应变累积速率在多大程度上可能是该地区有限的大地测量数据造成的。这些信息对评估与沿圣安德烈亚斯断层系统这一部分的断层运动有关的危险具有重要意义。为了解决这些问题，加州州立大学圣伯纳迪诺分校的研究人员和亚利桑那大学的同事们正在收集来自该地区的新的测量模式全球定位系统(GPS)数据，以便提供对圣安德烈亚斯断层圣贝纳迪诺和圣戈戈尼奥山口段目前弹性应变累积速度的精确估计。Sally McGill教授(加州州立大学圣贝纳迪诺分校)带领一个由本科生和高中教师(在他们的一些学生的陪同下)组成的团队，开展为期一周的年度活动，收集新的调查模式GPS数据。在2009年至2011年的每个夏季，该团队从圣贝纳迪诺山脉及其附近的25个地点收集了4至5天的GPS数据。这些数据由Sigrún Hreinsdóttir和Rick Bennett(亚利桑那大学)处理和建模，以及来自板块边界观测站(PBO)和南加州综合大地测量网络(SCIGN)的多达25个附近站点的同期GPS数据。该项目支持不同层次的本科生、高中教师和高中生。每年夏天，八名本科生和六名高中教师以及他们的一些学生都会参加为期一周的数据收集活动。麦吉尔与老师们合作开发海报和教案，将他们的研究经验带回课堂。每年，两名本科生都会利用GPS数据开发研究项目，并在整个夏天继续研究该项目，分析时间序列，并对断层滑移率进行一维弹性和弹性-粘弹性建模。他们在专业会议上展示成果，并被鼓励进入地球科学研究生院学习。特别努力从地球科学中代表性不足的人群中招收这些学生，这得益于加州州立大学圣贝纳迪诺分校是一所为拉美裔服务的机构，52名地质学专业的学生中有36%来自代表性不足的群体。这项提议的教育和外联部分正在由外部顾问罗伯特·德格鲁特进行评估。

Investigating disagreements between geologically and geodetically estimated slip rates for the San Bernardino and San Gorgonio Pass sections of the San Andreas fault. This award is supporting work aimed at better understanding the rate of slip along the southern San Andreas fault, in a region where highly discordant rates have been reported over different time intervals. The Holocene or latest Pleistocene slip rate (15 to 25 millimeters/year) of the San Bernardino section of the San Andreas fault is 3 to 5 times greater than rates based on elastic modeling of geodetic data (generally less than or equal to 5 millimeters/year). This is one of the largest known discrepancies between present rates of strain accumulation and the rate of Holocene to latest Pleistocene strain release. Does this discrepancy indicate that this section of the fault is no longer as active as it once was? Or is it a result of non-uniform rates of strain accumulation throughout the earthquake cycle? Geodetic data are sparse from the San Bernardino Mountains, along the northeast side of this section of the fault. Thus, before these questions about the cause of the rate discrepancy can be fully resolved, it is important to know to what extent the apparently low rate of geodetic strain accumulation may be an artifact of limited geodetic data in the region. Such information has important implications for assessing hazard associated with fault movement along this part of the San Andreas Fault System. To address these questions, researchers from California State University, San Bernadino an colleagues from the University of Arizona are collecting new survey-mode Global Positioning System (GPS) data from this region in order to provide a refined estimate of the present rate of elastic strain accumulation along the San Bernardino and San Gorgonio Pass sections of the San Andreas fault. Professor Sally McGill (California State University, San Bernardino) leads a team of undergraduate students and high school teachers (accompanied by some of their students) in an annual, week-long campaign to collect new survey-mode GPS data. During each summer from 2009-2011 the team collects 4 to 5 days of GPS data from 25 sites in the San Bernardino Mountains and vicinity. These data are processed and modeled by Sigrún Hreinsdóttir and Rick Bennett (University of Arizona), along with contemporaneous GPS data from up to 25 nearby stations from the Plate Boundary Observatory (PBO) and Southern California Integrated Geodetic Network (SCIGN) networks. This project supports undergraduate students, high school teachers and high school students at a variety of levels. Each summer, eight undergraduate students and six high school teachers with some of their students participate in the week-long data collection campaign. McGill works with the teachers to develop posters and lesson plans that bring their research experience back into the classroom. Each year, two of the undergraduate students develop research projects using the GPS data and continue working on the project throughout the summer, analyzing the time-series and conducting one-dimensional elastic and elastic-viscoelastic modeling for fault slip rates. They present results at professional meetings and are encouraged toward graduate school in the Earth sciences. Special efforts are made to recruit these students from populations that are under-represented in the geosciences, which is facilitated by the fact that California State University, San Bernardino is a Hispanic-serving institution at which 36 percent of the 52 geology majors are from under-represented groups. The education and outreach component of this proposal is being evaluated by an external consultant, Robert deGroot.