High‐resolution deep tectonic tremor locations beneath the San Andreas Fault near Cholame, California, using the double‐pair double‐difference location method

Abstract

AbstractWe determine high‐precision deep tectonic tremor locations beneath the San Andreas Fault (SAF) near Cholame, California, region by using a newly developed double‐pair double‐difference location method and a new 3‐D Vs model. Compared to the previous results, newly determined tremor locations are more consistent with known low‐frequency earthquake locations and are more concentrated along the SAF. New tremor locations near Cholame show clear contrast in the predominant depth of the tremor activity across the SAF and also show contrasts in the degree of periodic behavior both along and across the SAF. They collectively define a very special tremor generation region (VSTR) near the intersection corner between the SAF and the adjacent San Juan Fault (SJF). In the VSTR, new locations reveal some isolated tremor clusters, which may occur on multiple deep fault patches. For these isolated clusters, some are closer to the SAF and some are closer to the SJF, implying that both the SAF and SJF may extend to the ductile lower crust. Possible interaction between the SAF and SJF in the lower crust beneath the VSTR, combined with the trapped high‐pressure fluids, may explain the strong tremor activity, the isolated tremor clusters, and the characteristic tremor occurrence patterns and depth distributions in this region.