Abstract
AbstractInterpretations of dynamic processes and the thermal and chemical structure of the Earth depend on the accuracy of Earth models. With the growing number of velocity models constructed with different tomographic methods and seismic data sets, there is an increasing need for a systematic way to validate model accuracy and resolution. This study selects five shear wave velocity models in the U.S. and simulates full‐wave propagation within the 3‐D structures. Surface‐wave signals extracted from ambient seismic noise and regional earthquakes are compared with synthetic waveforms at multiple‐frequency bands. Phase delays and cross‐correlation coefficients between observed and synthetic waveforms allow us to compare and validate these models quantitatively. In general, measurements from regional earthquakes are consistent with ambient noise results, but appear more scattered, which may result from uncertainty of the earthquake source location, origin time, and moment tensor. Our results show the improvement of model prediction with the increase of seismic data sets and implement of advanced methods. There exists a positive linear trend between phase delay and interstation distance for three models, indicating that on average, these models are faster than the real Earth structure. The phase delays from the jointly inverted model of ambient noise and receiver function have negative means at all periods while without obvious dependence on the interstation distance. The full‐wave ambient noise tomographic model predicts more accurate phase arrivals compared to other models. This study suggests a need for an integrated model constructed with multiple seismic waveforms and consideration of anisotropy and attenuation.
Highlights
Seismic tomography has been one of the main methods to study the structure of the Earth
The cross-correlation coefficients from regional earthquakes are higher than from ambient noise (Figure 12), which means a better match of synthetic waveforms with observations
In general, for each model, the trend of phase delay versus interstation or source-receiver distance is consistent between ambient noise and regional earthquakes
Summary
Seismic tomography has been one of the main methods to study the structure of the Earth. The results showed that none of the Cascade models is adequately accurate in the sense that the misfits between the observed and predicted seismic waves are much larger than the uncertainty of the observed waveform, indicating room for significant improvement in the Cascade models. This earlier work suggests that it is necessary to assess and validate the existing velocity models of the United States in a systematic way. The phase delays and cross-correlation coefficients at multiple-frequency bands allow us to systematically and quantitatively compare these models
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