Collaborative Research: A Paleoseismic Record of Great Earthquakes on the Sunda Subduction Megathrust, Northern Sumatra

2004年12月26日有超过25万人丧生，揭示了印度洋地区易受毁灭性地震和海啸的影响。根据初步田野调查，在苏门答腊岛俯冲带最北端的苏门答腊岛沿海平原新发现的埋藏土壤含有2004年安达曼-亚齐地震前的全新世(10000年前至今)的证据。来自中央华盛顿大学、洪堡州立大学、宾夕法尼亚大学和印度尼西亚科学研究所和地球技术研究中心的一个研究小组正在研究这些矿床，以了解和记录苏门答腊岛最北部舜他巨型逆冲的全新世地震行为。通过整合古地震学、大地测量学、地质年代学和利用微化石重建古环境，该团队将建立苏门答腊岛北部近海苏门答腊岛俯冲带最北端的俯冲带年代学，其历史可以追溯到大约5000年前。结果将记录地震引起的快速下沉和海平面逐渐变化，在同震地面变化之前和之后。记录在案的相对海平面变化将有助于限制主俯冲带地震之前、期间和之后的滑动程度和程度。至少跨越三到四个地震周期的俯冲带地震的长期记录将对地震和海啸之间的平均时间提供现实的估计，类似于2004年12月袭击苏门答腊岛北部西海岸的地震和随后发生的海啸。初步工作表明，在海岸湿地地层学中存在古地震记录，湿地沉积物中既含有可测定日期的物质，又含有丰富的微化石，这将使人们能够重建俯冲带地震之前、伴随和之后海岸垂直陆地平面变化的时间和幅度。有文字记载的历史未能预警2004年12月26日舜他大地震和随之而来的海啸的可能性。在前期工作的基础上，研究小组确定了热带环境，在这些环境中，以前的大地震记录最有可能形成和持续。这些矿藏将产生数千年来俯冲带地震的长期记录，并将对地震和海啸之间的平均时间提供现实的估计，类似于2004年的地震和随后的海啸。该项目的成果将在苏门答腊岛沿海社区内以及与苏门答腊岛和国家政府机构一起传播。这些结果将证明，地震和海啸是应该预料到的反复发生的事件，需要进行灾害规划。

The loss of more than a quarter million lives on December 26, 2004 revealed the susceptibility of the Indian Ocean region to devastating earthquakes and tsunamis. Based upon preliminary fieldwork it now appears that newly discovered buried soils on the Sumatran coastal plain of northernmost part of the Sumatran subduction zone contain evidence for Holocene (10,000 years ago to the present) predecessors to the 2004 Andaman-Aceh earthquake. A research team from Central Washington University, Humboldt State University, the University of Pennsylvania, and the Indonesian Institute of Sciences and Research Center for Geotechnology are studying these deposits in order to understand and chronicle the Holocene seismic behavior of the Sunda megathrust of northernmost Sumatra. Through integration of paleoseismology, geodesy, geochronology, and paleoenvironmental reconstruction using microfossils, the team will establish a subduction zone chronology for the northernmost past of the Sumatran subduction zone offshore of northern Sumatra going back approximately five thousand years. The results will chronicle earthquake-induced rapid subsidence and gradual sea-level changes precursory to, and subsequent to, the coseismic land level changes. The documented relative sea-level changes will help constrain the extent and magnitude of slip before, during and after the main subduction zone earthquake. A long-term record of subduction zone earthquakes that spans at least three or four earthquake cycles will provide realistic estimates of the average time between earthquakes and tsunamis similar to the earthquake and ensuing tsunami that struck the west coast of northern Sumatra in December 2004. Preliminary work demonstrates that a paleoearthquake record is present in coastal wetland stratigraphy and that wetland sediment contains both datable material and abundant microfossils that will permit reconstruction of the timing and magnitude of vertical land level changes at the coast that precede, accompany and follow subduction zone earthquakes.Written history had failed to forewarn of the possibility of a giant Sunda megathrust earthquake and the resulting tsunami of December 26, 2004. Based on preliminary work, the research team has identified tropical environments where the record of former megathrust earthquakes is most likely to form and endure. These deposits will yield a long-term record of subduction zone earthquakes over thousands of years and will provide realistic estimates of the average time between earthquakes and tsunamis such similar to the 2004 earthquake and ensuing tsunami. Results from this project will be disseminated within the Sumatran coastal communities and with Sumatran and national governmental agencies. These results will establish that earthquake and tsunami are recurrent events that should be anticipated and that require disaster planning.