Data Set

Initially, a set of approximately 100,000 waveforms from 255 candidate earthquakes recorded by 1160 horizontal channels (Station-Network-Channel-Location, or SNCL labels are used to describe each) from the AZ, BK, CI and NC networks were extracted. The candidate events were selected from the CISN 2000-2006 seismicity catalog by gridding the state into 50km square bins and selecting the largest $M_{L}$ 3+ event that occurred in each bin, and also (to obtain an adequate USArray data set) the largest $M_{L}$ 3+ event in 2006 (or second largest if the largest 2000-2006 event event in the bin occurred in 2006). The SNCL channels included both broadband and strong motion instruments.

Local magnitude ($M_{L}$) was calculated from each channel's trace by deconvolving the instrument response and convolving the response of a Wood-Anderson seismograph (Uhrhammer et al, 1996). For each event, differences for all SNCL pairs were calculated, giving a dataset with more than 10 million differential observations. These differences were simultaneously inverted to determine a station adjustment for each SNCL, $dM_{L}$(SNCL), and a function describing the amplitude decay as a function of distance, called $\log{A_{o}}$.

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