Extracting Earth Models from Body-Wave Microseisms

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This project will study seismic noise and nontraditional seismic sources using advanced array signal processing algorithms that can extract information from weak signals. The work will help to characterize seismic noise sources and develop new methods to use them for resolving Earth structure. The main focus will be on P-wave microseisms from storms but the researchers will also examine non-volcanic tremor (NVT). One exciting aspect of the research is that noise analysis methods have the potential to be very useful in improving body-wave tomography for Earth structure, just as noise cross-correlation methods have recently proven successful in surface-wave tomography. A preliminary test examining teleseismic P waves recorded in southern California shows that similar arrival-time anomalies can be obtained both from direct P waves from a natural earthquake and P-wave noise generated by a large storm. In this case,the noise can be processed using waveform cross-correlation among different station pairs and optimal P relative arrival-time estimates can be computed using the same approach traditionally used to analyze earthquake arrival times. The investigators plan to experiment with taking advantage of non-traditional seismic sources(storms) to improve tomographic images by filling in the ray path coverage over certain azimuths. In addition, OBS observations may eventually provide the chance to extract absolute timing information of storm-generated P-wave microseisms, i.e., empirical Green?s functions, from ambient noise crosscorrelation.The proposed research will fundamentally advance our understanding of microseism generation and what microseisms tell us about storm activity and Earth structure. This research has the potential to track storms via a non-satellite approach, monitor intensities of storms, and contribute to inversions for deep Earth structure.