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Vp/Vs by Wadati and cluster events methods VELVET group

Vp/Vs by Wadati and cluster events methods VELVET group. Methods to compute Vp/Vs Using local earthquake data, the ratio between compressional and shear wave velocity (Vp/Vs) can be computed by using:

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Vp/Vs by Wadati and cluster events methods VELVET group

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  1. Vp/Vs by Wadati and cluster events methodsVELVET group

  2. Methods to compute Vp/Vs Using local earthquake data, the ratio between compressional and shear wave velocity (Vp/Vs) can be computed by using: Wadati method (Wadati, 1933; Kisslinger and Engdahl, 1973): application on a single event for the estimation of Vp/Vs as mean value along the path travelled by seismic rays. Similar earthquake method (Lin and Shearer, 2007): clusters of events with similar locations are combined for the estimation of Vp/Vs in the near source region.

  3. Using the Wadati method: - We are interested to identify Vp/Vs and possibly Vp, and Vs variations in time within the target volume; - We can analyze Vp/Vs through time for each event-station pair, thus identifying the directional properties of the elastic parameters of the medium and their temporal variation. - The identification of transient anomalies within the target volume can help in splitting subsets of data for time resolved seismic tomography.

  4. Basic Theory to compute Vp/Vs from Wadati method

  5. Application of L&S method - Synthetic tests show the relevance of P and S errors on the choose of the spatial extensions of cubic clusters: - Cluster of 1.0 km  Vp/Vs recovered if errors are within 0.01 s (i.e. manual Picks Weights= 0) - Cluster of 0.5 km  errors within 0.005 s (differential time by cross-correlation)

  6. Application of L&S method, in progress: - Reliable estimation of reading errors (P, S phases), differential data from cross-correlations?? - Differential data using only full weight P and S picks - Other types of “robust mean” to fit data Trimmed Least Squares - Spatial sampling of eqks with different locations (3D, DD)

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