Broadband Recording at the Site of Great Earthquake Rupture in the Alaska Megathrust

资金是在这个渴望的奖励下提供的，它将利用2011年夏天在R/V Langseth上一个已经获得资金的有源邮轮提供的机会。PI将在陆地上部署地震仪，覆盖孕震行为可变性最著名的例子之一--阿留申巨型逆冲的阿拉斯加半岛段，以记录活动震源激发，并将成像扩展到地震活动向下倾斜的极限之外。这艘由主动源资助的邮轮将沿着五个横断面拍摄巨型金字塔的图像。研究区东部在1938年的一次大地震(Mw=8.3)中破裂，现在显示出几乎完全的大地测量锁定。相比之下，西部位于舒马金峡谷，这是一个没有明显地震活动超过Mw=7.4的地点，大地测量数据表明那里有一个爬行的板块边界。这两个板块之间几乎没有其他变化：传入的太平洋板块在年龄和沉积堆积方面相似；上板块由相同的吸积地体构成；会聚几乎是弧形的。因此，拟议的阵列与有源激发相结合，将在受控背景下测试从锁定断层到蠕动断层的转换过程中巨型逆冲的更深层次结构。由于这两个转变(沿走向和向下倾斜)将被采样和成像，这些数据将提供一个强有力的测试概念，即巨型逆冲的结构特性控制地震发生的限度。在2011年夏季主动震源探险的拍摄期间，PI将部署9台宽带陆上地震仪，为期2个月，利用参加主动震源成像实验的船只和技术人员。这些仪器将部署在交通便利的简易机场。这些陆上仪器将极大地扩展有源阵列的口径。建议的数据将与配置的活动源数据一起以综合的方式进行分析和解释。广泛的影响：大型逆冲事件对阿拉斯加、卡斯卡迪亚和其他地方的城市中心构成重大地震危险。更好地了解孕震带的几何形状及其地震活动将减少环太平洋地区概率地震危险图中固有的不确定性。该研究区域还被认为对美国西海岸构成了最大的海啸风险，因为它靠近并具有方向性。这项工作还将有助于公众宣传地震危害，因为私人投资机构计划在试验期间访问实地城镇，以交流灾害和地震研究。这项研究计划作为OU一名学生研究生研究的一部分，并将提拔一名来自代表不足的群体的职业生涯早期教师。

Funds are provided under this EAGER award that will capitalize on an opportunity provided by an already funded active-source cruise on the R/V Langseth in the summer of 2011. The PI will deploy seismometers on-land across one of the best-known examples of variability in seismogenic behavior - the Alaska Peninsula segment of the Aleutian megathrust to record the active-source shots and extend imaging beyond the down-dip limit of seismicity. The funded active-source cruise will image the megathrust along five transects. The eastern part of the study area ruptured in a great (Mw=8.3) earthquake in 1938, and now shows nearly full geodetic locking. By contrast, the western part lies in the Shumagin Gap, a site of no clear seismicity larger than Mw=7.4, and where geodetic data suggest a creeping plate boundary. Little else changes between the two segments: the incoming Pacific plate is similar in age and sediment accumulation; the upper plate is constructed of the same accreted terranes; and convergence is nearly arc-normal. Thus, the proposed array, combined with active-source shots, will test in a controlled setting the deeper structure of megathrusts across the transition from locked to creeping faults. Because these two transitions (along-strike and down-dip) will be sampled and imaged, these data will provide a strong test of the notion that structural properties of the megathrust control limits to seismogenesis. The PI will deploy 9 broadband onshore seismometers for 2 months during shooting of the active-source expedition in summer 2011, taking advantage of the ship and technical staff present for the active-source imaging experiment. These instruments will be deployed at easily-accessible airstrips. These on-land instruments will greatly extend the active-source array aperture. The proposed data will be analyzed and interpreted together with the collocated active-source data in an integrated fashion.Broader Impacts: Megathrust events pose significant seismic hazard to urban centers in Alaska, Cascadia, and elsewhere. Better knowledge of the geometry of seismogenic zones and their seismicity will reduce the inherent uncertainty in probabilistic seismic hazard maps around the Pacific Rim. The study area is also considered to pose the greatest tsunami risk to the west coast of the US because of its proximity and orientation. This work will also help public outreach on earthquake hazards as the PIs plan to visit towns in the field area during the experiment to communicate hazards and earthquake research. The study is planned to be part of the graduate research for a student at OU, and will promote as PI an early-career faculty member from an underrepresented group.