Hydroacoustic events located at the intersection of the Atlantis (30°N) and Kane (23°40′N) Transform Faults with the Mid‐Atlantic Ridge
Hydroacoustic events located at the intersection of the Atlantis (30°N) and Kane (23°40′N) Transform Faults with the Mid‐Atlantic Ridge
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位于亚特兰蒂斯 (30°N) 和凯恩 (23°40′N) 转换断层与大西洋中脊交汇处的水声事件
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发表时间：
2006
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通讯作者：
Deborah K. Smith
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作者：
Clare M. Williams;R. Stephen;Deborah K. Smith
我们研究了位于大西洋中脊两段两端的T相事件的特征。我们进行这项研究的动机是了解T相位置是否代表地震震中（从而是否可以从其空间模式中做出准确的地质推断），并进一步了解T相事件特征与地震属性之间的关系。我们研究了158个T相事件的特征，包括事件位置、水深和源到接收器的距离。还对T相的传播路径进行了建模，以研究遇到海底地形的影响。我们发现现有的T相激发和传播模型不能充分解释我们所有的观察结果。水听器的T相振幅（接收电平）显示不依赖于事件水深，与预测事件量级随水深增加而减小的电流激励模型相反。观察到的接收电平随着源到接收器的距离的增加而减少，并且一旦考虑到衰减，来自两个研究区域的事件在水听器之间的相对接收电平中表现出不同的趋势。我们的声线跟踪模型能够基于事件和每个水听器之间的一维地形再现水听器相对振幅的类似趋势，但观测数据和模型的方差都很高。我们观察到浅水事件的短T相起始时间和深水事件的长起始时间的模式，其中起始时间被定义为T相包络出现在环境噪声之上与其第一个峰值之间的时间间隔。这表明，发病时间可能是一个函数的几个变量，包括效率的能量转换的基础上，当地地形，传播效率的基础上事件水深，震源深度在地壳中。本研究的结果强调了T相激发和传播的复杂性，并认为需要改进T相激发和传播的当前模型，以解释T相数据的观测特征。
We investigate the characteristics of T‐phase events located at the ends of two segments of the Mid‐Atlantic Ridge. Our motivations for the study were to understand whether T‐phase locations represent earthquake epicenters (and thus whether accurate geological inferences can be made from their spatial patterns) and to understand further the relationship between T‐phase event characteristics and earthquake properties. We examine the characteristics of 158 T‐phase events with respect to both event location water depth and source to receiver distance. The propagation paths of the T‐phases are also modeled to study the effects of encountering seafloor topography. We find that existing models for T‐phase excitation and propagation cannot explain adequately all of our observations. The amplitudes (Received Levels) of T‐phases at the hydrophones show no dependence on event water depths, in contrast to current excitation models which predict a decrease in event magnitude with increasing water depth. The Received Levels are observed to decrease with increasing source to receiver distance, and events from the two study areas exhibit different trends in relative Received Levels between hydrophones, once attenuation is taken into account. Our acoustic ray trace model is able to reproduce similar trends in relative amplitudes at the hydrophones based on 1‐D topography between the event and each hydrophone, but the variances in both the observed data and model are high. We observe a pattern of short T‐phase onset times for shallow water events and long onset times for deep water events, where onset time is defined as the time interval between the appearance of the T‐phase envelope above the ambient noise and its first peak. This suggests that the onset time may be a function of several variables, including efficiency of energy conversion based on local topography, efficiency of propagation based on event water depth, and hypocentral depth in the crust. The results of this study underscore the complexity of T‐phase excitation and propagation and argue that current models of T‐phase excitation and propagation need to be improved to explain the observed characteristics of T‐phase data.