The Salton Trough cluster now contains many more events and covers a wider area.
The Salton cluster is named for the Salton Trough in southeastern
California, a transitional region between sea-floor spreading in the
Gulf of California and the San Andreas transform fault system on land.
The largest event is 5.5 Mw for the July 7, 2010 earthquake. Only events
recorded to at least 10° epicentral distance were retained. Station
coverage for direct calibration is superb since about 2009 but events
prior to about 2007 could not be kept in the cluster because of poor
connectivity with the modern dense network in the area. Because of the
dense network coverage. Free-depth relocation was used to determine the
focal depth for most events (which were held fixed in the final runs),
but a few focal depths were adjusted manually to better fit the
near-source arrival time data. The cluster covers both sides of the
transform fault zone, as well as events in the fault zone itself, and
crustal heterogeneity is very evident in the arrival time dataset.
Because of the immense number of close-in data (~6000 readings for the
hypocentroid) the calibrated epicenters have quite small confidence
ellipses but it is likely that the true uncertainties are greater due to
the strong crustal heterogeneity. All events have depth control from
near-source and local-distance readings, and a few have depth estimates
from teleseismic depth phases which are in good agreement.