RAPID: Seismo-acoustic radiation from a local earthquake aftershock sequence: how, when, and why seismic waves cross the ground-atmosphere interface

RAPID：当地地震余震序列的地震声辐射：地震波如何、何时以及为何穿过地面-大气界面

基本信息

批准号：
2029940
负责人：
Thomas Mikesell
金额：
$ 7.36万
依托单位：
Boise State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-01 至 2021-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2029940&HistoricalAwards=false
关键词：
RAPID Seismo acoustic radiation local

项目摘要

Central Idaho experienced a rare large earthquake (M6.5, depth ~14 km) on the evening of March 31, 2020 (local time). This is the second-largest ever recorded earthquake in Idaho, and because earthquakes of this magnitude are uncommon, the prospect of recording a valuable aftershock sequence motivated Boise State University researchers to set up a sensor network the following day in an area near to the epicenter. This deployment included both seismometers (to measure seismic waves underground) and infrasound sensors (to measure pressure waves in the air). This new network greatly enhances the detection capacity to the more than 283 M2.5+ aftershocks that have already been recorded by the distant regional seismic network. In addition, this new network will significantly improve the accuracy of aftershock locations, which will allow us to understand and map the fault distribution in the area and better anticipate future earthquake hazards, including potential large earthquakes that could come in the following weeks and months. In addition to tracking the seismic radiation from these aftershocks, preliminary analyses from the monitoring of infrasound, or low frequency pressure waves in the atmosphere, has revealed the production of an incredible amount of earthquake ‘sounds’. These air waves have been identified at multiple sites across the geophysical network, and early analyses indicate that they originate in the surrounding mountains as the mountains shake during the passage of the seismic waves. Past observations of mountain-generated air waves have only been studied at long distances; therefore, scientists know very little about the process of earthquake sound generation. Thus, monitoring the Stanley, Idaho aftershock sequence by expanding and maintaining the local geophysical sensor network will provide a unique and fleeting chance to study not just this region’s earthquakes, but also the transmission of seismic energy to the air (and vice versa). An improved understanding of earthquake-generated air waves may lead to new methods of monitoring seismic hazards, including secondary hazards in mountainous regions like avalanches and rockfalls, benefiting the communities exposed to such hazards and the agencies that must respond to them.Aftershocks of Central Idaho’s recent large earthquake (March 31 2020, M6.5, depth ~14 km) provide an ephemeral and unique opportunity to understand topographic seismic-acoustic energy conversion. Motivated by the rarity of events of this magnitude in Idaho, a team of researchers from Boise State University (BSU) began deploying seismometers and infrasound sensors in the region surrounding the epicenter the following day, resulting in a sensor network with excellent spatial coverage. The BSU network includes several spatially dispersed sites including both seismic and acoustic arrays (closely-spaced clusters of sensors that can identify correlated signals and determine the wave’s propagation vector), enabling it to identify backazimuths to wave sources that can be mobile, low in amplitude, continuous, or with emergent onsets. Additionally, because some infrasound sensors and seismometers are co-located, it will be possible to determine the mutual responses of seismic and acoustic instruments to acoustic and seismic waves. Early results from the temporary BSU network include aftershocks that are not detected on permanent regional stations as well as frequent earthquake-generated infrasound. Earthquake-generated infrasound is observed at multiple sites, is not associated with rock falls or avalanches, and appears to originate in nearby mountainous topography during the passage of seismic waves. Such infrasound has previously only been observed at regional distances where atmospheric propagation effects are strong, limiting the resolution of source inferences; the BSU network does not suffer from this limitation. Maintaining and expanding the BSU seismo-acoustic network during the aftershock sequence can elucidate the conversion of wave energy between the ground and atmosphere in unprecedented detail. This improved understanding of earthquake-generated infrasound will include topics like controls on infrasound generation (e.g., dependence on earthquake magnitude and depth, topographic properties, and seismic wave type), infrasound properties (e.g., radiation patterns and duration), coupling of earthquake-generated infrasound back into the ground, instrumentation sensitivities (e.g., the response of seismometers to infrasound and of infrasound sensors to ground motion), and analytical methods for locating earthquake infrasound sources. Earthquake-associated topographic infrasound could serve as a new monitoring method in earthquake-prone mountainous areas. Due to the need to distinguish earthquake-related mountain infrasound from secondary seismic hazards like avalanches or rock falls, an improved understanding of earthquake infrasound will help communities and agencies affected by such hazards.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

爱达荷州中部在2020年3月31日晚上（当地时间）经历了罕见的大地震（M6.5，深度约14公里）。这是爱达荷州有史以来第二大地震，并且由于如此巨大的地震并不常见，因此记录有价值的余震序列的前景，激发了博伊西州立大学的研究人员在第二天在震中附近的地区建立传感器网络。这种部署包括两个地震仪（测量地下的地震波）和反向传感器（测量空气中的压力波）。这个新的网络大大提高了遥远区域地震网络已经记录的283 M2.5+余震的检测能力。此外，这个新的网络将显着提高余震位置的准确性，这将使我们能够理解和绘制该地区的断层分布，并更好地预期未来的地震危害，包括可能在接下来的几周和几个月中发生的潜在大地震。除了跟踪这些余震中的地震辐射外，还通过监测侵袭者或大气中的低频压力波进行了初步分析，还揭示了产生了令人难以置信的地震“声音”。这些气波已在地球物理网络的多个地点鉴定出来，并且早期的分析表明，随着地震波的通过期间，山脉摇晃，它们起源于周围的山脉。过去对山区生成的空波的观察仅在长距离的情况下进行了研究。因此，科学家对地震声的过程一无所知。通过扩展和维护当地的地球物理传感器网络来监视史丹利，爱达荷州余震序列，将为不仅研究该地区的地震，而且还将地震能量传播到空中（以及VICE FERSA）。对地震生成的空气波的深入了解可能会导致新的监测地震危险的方法，包括诸如雪崩和岩石之类的山区危险，使暴露于此类危害的社区和必须对其做出反应的机构受益。地形地震声能转换。由爱达荷州（BSU）的一组研究人员的团队开始在第二天的地区围绕震中的地区部署地震仪和侵权传感器，从而导致传感器网络具有出色的空间覆盖，从而在爱达荷州的稀有事件中稀有，开始了地震仪和侵权传感器。 BSU网络包括几个空间分散的位点，包括地震阵列和声学阵列（传感器的紧密间隔簇，可以识别相关信号并确定波浪的传播向量），从而使其能够识别可为波动源识别为可移动的源源物，在放大器中，持续，或与新兴的网络相处。此外，由于某些触发传感器和地震仪是共同的，因此有可能确定地震和声学仪器对声学和地震波的相互响应。临时BSU网络的早期结果包括在永久区域站未检测到的余震以及经常生成地震的临时。在多个地点观察到地震生成的凸起，与岩石瀑布或雪崩无关，在地震波的通过期间似乎源于近山地形。以前仅在大气传播效应强烈的区域距离上观察到这种伸展，从而限制了源信息的分辨率。 BSU网络没有受到这种限制的困扰。在余震序列中维持和扩展BSU地震声网络可以以前所未有的细节阐明地面和大气之间波能的转化。这种对地震生成的插音的这种深入的了解将包括主题，例如对插道产生的控制（例如，对地震幅度和深度的依赖性，地形和地震波类型），插向特性（例如，辐射模式和持续事件），辐射模式和持续时间，持续时间），地震构成了地震的响应，并响应了地震的响应。伸向地面运动的非传动传感器以及用于定位地震内部源的分析方法。与地震相关的地形相关的地形可能可以作为地震易于地震山区的新监测方法。由于需要将与地震相关的山地保险与诸如雪崩或岩石瀑布之类的次要地震危害区分开，对地震侵袭的了解将有助于社区和受这种危害影响的社区和机构。该奖项反映了NSF的法规任务，并被认为是通过基金会的知识优点和广泛的cristria criperia criperia criperia crighia the Insportaucation通过评估来获得的支持。