Mapping the Sources of Proximal Earthquake Infrasound
Mapping the Sources of Proximal Earthquake Infrasound
复制标题
DOI：
10.1029/2020gl091421
复制
发表时间：
2020-11-28
影响因子：
5.2
通讯作者：
Liberty, L. M.
中科院分区：
文献类型：
--
作者：
Johnson, J. B.;Mikesell, T. D.;Liberty, L. M.
我们于2020年4月7日在美国爱达荷州记录了一次M(WR)3.6级地震，使用了六个三元次声阵列网络和位于震源25公里范围内的同址宽带地震仪。次声阵列处理用于识别地震-大气耦合相位的到来和长达90秒的次声尾波。视速度范围从地震速度到亚水平大气声速都归因于到达阵列的重合波的叠加。我们发现，到达的次声起源于偏离震中后方位角的大范围后方位角，这表明在这次相对较小的地震中，二次辐射体无处不在。二次辐射体通常位于高架地区，利用反演和地震起爆时间进行识别。近端地震次声源分析可用于绘制地震动分布图，对地震危险性评价具有重要意义。众所周知，地震会产生声音，这些声音的频率既可感知，又低于人类听觉的阈值。低频地震（次）声可以用专门的麦克风记录下来，以了解地震是如何震动地球表面的。我们的研究使用6个次声传声器站来探测和定位发生在距这些站25公里范围内的3.6级地震的声源。记录的次声是由次声站的地面震动产生的，也是在与山区地形相吻合的广泛分布地区产生的。当地震波经过时，这些地震声音的次级源就会出现，由此产生的地面震动扰乱了大气。在本研究中，即使地震规模相对较小，次声识别也是可能的。
We recorded a M(WR)3.6 earthquake in Idaho (USA) on 7 April 2020 with a network of six three-element infrasound arrays and co-located broadband seismometers situated within 25 km of the hypocenter. Infrasound array processing is used to identify the arrival of seismic-to-atmospheric coupled phases and as much as 90 s of infrasound coda. Apparent velocities ranging from seismic speeds to subhorizontal atmospheric sound speeds are attributed to a superposition of coincident waves arriving at the arrays. We find that the arriving infrasound originates from a broad range of back azimuths that deviates from epicentral back azimuth and indicates the ubiquity of secondary radiators for this relatively small earthquake. Secondary radiators, which often locate in regions of elevated topography, are identified using backprojections and earthquake initiation time. Analysis of infrasound sources from proximal earthquakes can be used to map ground shaking distributions, which are important for assessment of earthquake hazards.Plain Language Summary Earthquakes are known to produce sounds, which encompass frequencies that are both perceptible and below the threshold of human hearing. Low frequency earthquake (infra)sound may be recorded with specialized microphones to understand how earthquakes shake Earth's surface. Our study uses six infrasonic microphone stations to detect and locate sound sources for a magnitude 3.6 earthquake that occurred within 25 km of the stations. The recorded infrasound is produced by ground shaking at both the infrasound stations and also over a wide distribution of areas coinciding with mountain topography. These secondary sources of earthquake sounds occur as seismic waves pass by and the resultant ground shaking perturbs the atmosphere. The identification of infrasound in this study is possible even though the earthquake size is relatively small.