FAULT-ZONE STUDIES OF THE M9 TOHOKU-OKI, JAPAN EARTHQUAKE SEQUENCE

日本东北冲 M9 地震序列的断层带研究

• 批准号: 1142020
• 负责人: Donald Helmberger
• 金额: $ 18.11万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1142020&HistoricalAwards=false
• 关键词: FAULT; ZONE; STUDIES; M9; TOHOKU

One of the grand challenges for the seismology community involves slippage along plate boundaries. Energy released from many years of locking along subduction zones is made particularly difficult to understand since they occur beneath the deepest portions of the oceans. But they are very important because large subduction zone earthquakes pose one of the greatest natural hazards to mankind, either by strong shaking, flooding (tsunami), or a combination of both, i.e., the recent Tohoku-Oki Earthquake. Rupture properties of these rare events are poorly understood, especially Tsunamigenic Earthquakes (TE) with little pre-tsunami shaking such as the 1896 Sanriku earthquake. The well recorded 2011 Tohoku-Oki earthquake sheds some new light on these issues where a generic interplate event at depth appears to have triggered a rare TE event. Recent reports indicate that the strong shaking came from rupture at depth 30km with relatively small magnitude (Mw~8.5) with 3D amplification occurring primarily at relatively short-periods (2-10 sec) and higher, whereas, the flooding was caused by the large displacement (Mw~9) close to the trench (50m) and was dominated by relatively long-period ( 20 sec) radiation. The mixture of these rupture styles presents significant challenges in the analysis and modeling of this earthquake and requires data sets covering a broad range of periods. Fortunately, the data coverage on the Japanese Islands is remarkable providing the best set of observations ever recorded for both the main event and the many aftershocks. The investigators will use high-resolution waveform modeling to investigate the variation in fault zone structure in an attempt to understand the great variation in rupture properties both along strike and as a function of depth.The work is a program of technique development along with broadband inversions of the Tohoku-Oki earthquake sequence. The basic aim is to address the locations and source parameters of these events embedded in a 3D structure, exploiting our semi-automated Cut-and-Paste (CAP) method for regional data (0 to 400 km) and CAPt at teleseismic distances. Joint inversions will be used to establish the most transparent paths to arrays for extending the broadband inversions of the main event and large foreshocks and aftershocks.

地震学界面临的最大挑战之一是板块沿着边界的滑动。由于俯冲带位于海洋最深处，因此，人们对多年来沿着俯冲带锁定所释放的能量的理解变得特别困难。但它们非常重要，因为大型俯冲带地震对人类构成了最大的自然危害之一，无论是强烈的震动，洪水（海啸），还是两者的结合，即，最近的东北冲地震。这些罕见事件的破裂特性知之甚少，特别是海啸前几乎没有震动的海啸地震（TE），如1896年的三陆地震。记录良好的2011年东北冲地震为这些问题提供了一些新的线索，其中一个深层的一般板间事件似乎引发了一个罕见的TE事件。最近的报告表明，强烈地震来自深度30 km的破裂，震级相对较小（Mw~8.5），3D放大主要发生在相对短的周期（2-10秒）和更高的时间内，而洪水是由大位移引起的（Mw~9）靠近海沟（50 m），并以相对长周期（20秒）辐射为主。 这些破裂类型的混合物在这次地震的分析和建模中提出了重大挑战，需要涵盖广泛时期的数据集。幸运的是，日本群岛上的数据覆盖范围非常可观，为主震和许多余震提供了有史以来最好的观测记录。研究人员将使用高分辨率波形模拟来调查断层带结构的变化，试图了解破裂性质在沿着走向和深度函数上的巨大变化。这项工作是一项技术开发计划，沿着与东北冲地震序列的宽带反演。其基本目的是解决嵌入在三维结构中的这些事件的位置和源参数，利用我们的半自动剪切和粘贴（CAP）方法的区域数据（0至400公里）和CAPt在近距离。联合反演将被用来建立最透明的路径，以阵列扩展的宽带反演的主要事件和大的前震和余震。