Ambient Near-Coastal Seismic Noise and Temporal Monitoring

研究人员将利用二次海洋微震噪声的位置来提高地壳速度变化的时间分辨率，并绘制主海浪海岸反射的位置。所提出的微震震源定位技术是基于一种实时地震定位算法，适用于南加州等地区，在这些地区，多个同时震源位于离岸几百公里内，陆地上有分布良好的地震台阵。源位置的使用克服了标准相关方法的一个问题，即需要随机分布的源来实现精确的测量，这意味着长的相关时间，因此降低了时间分辨率。利用一组震源位置，可以在对比中使用较短的合成地震记录.利用高分辨率波作用模型（WAM）确定的入射波场和假设的反射源形成一个伴随问题来确定海岸反射点，并用合成和真实的数据实例说明了源定位过程。结果表明，在任何给定的时刻，往往有多个震源点活动。它们提供了两种独立的方法：（1）合成孔径雷达（SAR）测量的强度波波相互作用的源区？是产生脉动的必要条件。一个新的机载系统将于2008年6月在近海S。加州寻找相反的海洋波场，这是源点的指示。(2)利用震源位置和海洋微地震理论计算的观测到的微地震振幅和估计的阻尼振幅之间的比较。这项研究将提供机会，开发一个模型，这一过程，并最终产生一个完整的波场，可以纳入下一代的波作用模型。微震提供了一种手段，连续监测瑞利波速度在整个洛杉矶盆地作为一个潜在的代理应力变化。在这一过程中使用的源增加了时间分辨率，并消除了系统偏差的问题，由于随机源位置的假设。这项研究桥梁三个社区：雷达干涉测量，海洋学和地震学，因此有可能刺激在所有这些领域的研究。确定海岸反射的机制将大大增强连续性波浪作用模型。适用于南加州的应用程序可以扩展到其他几个地区，包括北方加州，卡斯卡迪亚和日本。这项研究建立的程序可以成为南加州标准地震监测的一部分

The researchers will use the locations of secondary ocean microseisms noise to improve thetemporal resolution of changes in crustal velocity, and to map the locations of coastalreflections of primary ocean waves. The proposed microseisms source location techniqueis based on an algorithm developed for real-time earthquake locations and is suitable forareas like Southern California where multiple simultaneous sources are located within afew hundred km offshore and where there is a well distributed seismic array on land. Theuse of source locations overcomes a problem with standard correlation methods thatrequire a random distribution of sources to achieve precise measurements, whichtranslates to long correlation times and hence a reduced temporal resolution. Using a setof source locations, a shorter synthetic seismogram can be used in the correlation. Thecoastal reflection points will be determined by forming an adjoint problem with thehypothesized reflection source and an incident primary wavefield determined from high resolutionWave Action Models (WAM's).The source locations procedure is demonstrated with both a synthetic and real dataexamples. The results show that there are often many source points active at any giventime. They provide two independent approaches: (1)Synthetic Aperture Radar (SAR) measurements of the intensity of wave-waveinteractions at the source regions ? a necessary condition for microseisms generation. Anew airborne system that will be flown in June 2008 over the offshore S. California tolook for opposing ocean wavefields which are indicative of the source points. (2) Acomparison between the amplitudes of the observed micoseisms and estimatedamplitudes calculated using the source locations and the theory of ocean microseisms.The nature of thecoastal reflections is currently poorly understood. This research will provide theopportunity to develop a model for this process and to ultimately to generate a descriptionof the complete wave-field that can be incorporated into the next generation of WaveAction Models. Microseisms provide a means to continuously monitor the Rayleighwave speed across the Los Angeles basins as a potential proxy for stress changes. Theuse of sources in this procedure increases the temporal resolutions and removes theproblem of systematic bias due to the assumption of random source locations.This research bridges three communities: radar interferometry,oceanography and seismology and hence has the potential to spur research in all theseareas. Determining the mechanisms for coastal reflections will significantly enhance thecommunity wave action models. The application to southern California can be extendedto several other areas including northern California, Cascadia, and Japan. The procedureestablished by this research could become part of the standard seismic monitoring ofSouthern California