Collaborative Research: Paleoseismic Histories of Southwest Pacific Plate Boundaries from Precise Mass Spectrometric 230 th/234U Dating of Uplifted Corals

过去地震的时间、大小和破裂几何学的历史为确定过去的地震周期性和预测未来的活动提供了最直接的依据。然而，地震学记录的地震历史对于这种方法来说太短了。西南太平洋瓦努阿图的一些海岸在每次板间冲断带地震时都会隆起，这种隆起会将浅海珊瑚群落抬高到海平面以上，并将它们杀死。这些事件特有的珊瑚形态，结合最近改进的热电离质谱230测年，使精确测定这些事件的年龄成为可能，从而确定同震隆升历史。该项目与EAR89-04705合作，将在瓦努阿图中部的几个地段收集一套显示隆起-杀戮形态的珊瑚，并进行230岁年龄测定。由于瓦努阿图被认为是一个弱耦合俯冲带，计算结果将有助于计算地震滑动与地震滑动的比例，并确定在地震周期的哪个时间点发生无地震滑动。

The history of timing, size and rupture geometry of past earthquakes provide the most direct basis on which to determine past seismic periodicity and to predict future activity. However, seismographically recorded earthquake histories are too short for this approach. Some coasts in Vanuatu, Southwest Pacific, uplift during each interplate thrust zone earthquake, and the uplift raises shallow-living coral colonies above sea level and kills them. The characteristic coral morphology of these events, combined with recently refined thermal ionization mass spectrometric 230th dating makes it possible to date these events precisely and thereby determine the coseismic uplift history. This project, collaborative with EAR89-04705, will collect a suite of corals showing uplift-kill morphology along several segments of central Vanuatu and conduct 230th age dating. Results will allow calculation of coseismic uplift periodicity and since Vanuatu is considered a weakly coupled subduction zone, results will also help in calculating the proportion of aseismic vs. seismic slip and determine at what point in the earthquake cycle the aseismic slip occurs.