Testing the processing sequence

Data collected by () was designed to record the interface response and coseismic energy separately as a test data set for processing. However, these files lack any additional interface response events after the onset of coseismic energy (Figure a). In an electroseismic data set collected with a standard geometry, we would be looking for interface response events within the coseismic energy. For that reason, we followed the example of () and constructed a test data file by windowing out (Figure b) the interface response from a record (Figure a) using a sin² taper in the time direction and adding it to the original file within the coseismic energy. We did this twice (Figure c), adding the synthetic arrival at two different times in the record. The resulting record (Figure d) appears essentially identical to the original file, but contains two interface response events hidden within to test our methodology.

 

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Figure 6 (a) Data file. (b) Interface response (IR) from (a), windowed with sin² taper. (c) Two IR events to be added to data. (d) Test data- starting data plus two added events.

Using the PEF design windows shown (Figure b and c), and the parameters mentioned above, we solve the inverse problem (equation ). Figure d shows 363#363, our best estimate of 343#343, the component of the data that is made up of the interface response energy. The two added interface response events are evident, as is the original interface response. Unfortunately, a considerable amount of dipping coseismic energy still remains between 0.025 and 0.04 seconds, and the added event below 0.06 seconds is somewhat weak. Despite these shortcomings, the final result (Figure d) is considerably better than the original data file (a).

 

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Figure 7 (a) Data file (windowed version of file in d). (b)Window to be used for determination of signal PEF 332#332. (c)Window used for determination of noise PEF 338#338. (d) Output of processing, 357#357. Note that added horizontal events 0.045 s and 0.065 s are visible.