Retrieving impulse response function amplitudes from the ambient seismic field

Abstract

Seismic interferometry is now widely used to retrieve the impulse response function of the Earth between two distant seismometers. The phase information has been the focus of most passive imaging studies, as conventional seismic tomography uses traveltime measurements. The amplitude information, however, is harder to interpret because it strongly depends on the distribution of ambient seismic field sources and on the multitude of processing methods. Our study focuses on the latter by comparing the amplitudes of the impulse response functions calculated between seismic stations in the Kanto sedimentary basin, Japan, using several processing techniques. This region provides a unique natural laboratory to test the reliability of the amplitudes with complex wave propagation through the basin, and dense observations from the Metropolitan Seismic Observation network. We compute the impulse response functions using the cross correlation, coherency and deconvolution techniques of the raw ambient seismic field and the cross correlation of 1-bit normalized data. To validate the amplitudes of the impulse response functions, we use a shallow M w 5.8 earthquake that occurred on the eastern edge of Kanto Basin and close to a station that is used as the virtual source. Both S and surface waves are retrieved in the causal part of the impulse response functions computed with all the different techniques. However, the amplitudes obtained from the deconvolution method agree better with those of the earthquake. Despite the expected wave attenuation due to the soft sediments of the Kanto Basin, seismic amplification caused by the basin geometry dominates the amplitudes of S and surface waves and is captured by the ambient seismic field. To test whether or not the anticausal part of the impulse response functions from deconvolution also contains reliable amplitude information, we use another virtual source located on the western edge of the basin. We show that the surface wave amplitudes of the anticausal part agree well with those of a shallow M w 4.7 event that occurred close to the virtual source. This study demonstrates that the deconvolution technique seems to be the best strategy to retrieve reliable relative amplitudes from the ambient seismic field in the Kanto Basin.

Amplification and Attenuation Across USArray Using Ambient Noise Wavefront Tracking

“…In such virtual source reconstructions, the authors are careful to only consider station‐station paths over a narrow range of azimuths and are careful to stack all NCFs over a consistent time period, thus mitigating potential biases from inhomogeneous noise source distributions. Viens et al () also demonstrate that while temporal and azimuthal variations in noise source may contribute to variability in NCF amplitudes, such errors are small compared to the large effect of sedimentary basin amplifications they observe, indicating that direct observation can still be useful in some contexts.…”

Coherence‐Based Approaches for Estimating the Composition of the Seismic Wavefield

“…Particular attention has been paid to understand the effect that the inhomogeneous distribution of noise sources would have on the coherence or cross‐correlation measured between stations, with the goal of determining whether measurements can be reliably used for the study of seismic velocities or attenuation (e.g., Cupillard & Capdeville, ; Harmon et al, ; Lawrence & Prieto, ; Tsai, , ; Weaver, ; Yang & Ritzwoller, ), with additional studies exploring the extent to which signal preprocessing can reduce the effect of inhomogeneous noise sources (e.g., Bensen et al, ; Viens et al, ). Some of these velocity or attenuation measurements require a great amount of precision and stability over time (Froment et al, ), such as for the observation of material velocity changes; velocity variations on a daily or monthly time scale may be as small as a couple percent but have been shown to yield valuable information regarding temperature or pore pressure changes (i.e., Brenguier et al, ; Lecocq et al, ; Taira & Brenguier, ).…”

Investigating the Capability to Extract Impulse Response Functions From Ambient Seismic Noise Using a Mine Collapse Event

“…Using data from the shallow‐depth mine collapse event, we have more thoroughly demonstrated the capability to retrieve IRFs from an ambient seismic field absent a correction for the occurrence depth or source mechanism. Viens et al () also demonstrated that the sensitivities of retrieved amplitudes to seasonal variations are relatively small throughout the year for the deconvolution method. These findings correspond with the results of this study.…”

“…Geophysical Research Letters 10.1002/2017GL075532 absent a correction for the occurrence depth or source mechanism. Viens et al (2017) also demonstrated that the sensitivities of retrieved amplitudes to seasonal variations are relatively small throughout the year for the deconvolution method. These findings correspond with the results of this study.…”