Crustal structure modeling of earthquake data: 1. Simultaneous least squares estimation of hypocenter and velocity parameters

Abstract

Arrival times from an ensemble of discrete earthquakes independently contain information on hypocenter locations and jointly provide information on the velocity model. A properly formulated least squares estimation procedure can be used to determine simultaneously both hypocenter and velocity model parameters. By means of this procedure a sufficiently well distributed set of earthquakes provides information on crustal structure without some of the inherent difficulties associated with explosion refraction interpretation. Useful error estimates and resolving information are provided, and tests on artificial data indicate that successful inversions are obtainable, even for models with low-velocity zones, by using only P wave first arrivals at a number of stations. The method may have application for detecting P wave low-velocity regions resulting from dilatancy and is directly extendable to modeling shear wave velocity structure when S arrivals are used in place of P arrivals. $TA STA STA ß ß . . . ß / ,,, ,,-r ,-,. / :0-' HYPOCENTER \ ,

Seismic velocity structure and microearthquake source properties at The Geysers, California, geothermal area

“…These results are not used to support arguments that a particular feature exists and has acceptable error; they help to highlight features that should be viewed with skepticism due to inherent trade-oft's or instabilities. This approach has been used frequently (Crosson, 1976;Aki and Lee, 1976;Spencer and Gubbins, 48 1980;Thurber, 1983) and could be -called "quelling by-parameterization", not a particularly rigorous approach, but one that has proved useful.…”

“…For example, Crosson (1976) Cormulated a procedure that solved Cor hypocenter perturbations and velocity perturbations simultaneously; that is, all parameter perturbations are determined at once using a Cull matrix solution. He solved a matrix equation of the Corm oC (2.13) (excluding station correction terms), in an iterative least squares approach.…”

Accurate hypocentre locations in the Middle-Durance Fault Zone, South-Eastern France

“…The dependence on hypocentral parameters and seismic velocity is called the coupled hypocentrevelocity model problem [1,31,32]. It can be linearized and written in matrix notation as [3]:…”

Earthquake hazard evaluation in the Pacific Northwest

“…Table 1 of the second report (Crosson, 1975) shows the revised crustal velocity structure used in the determination of earthquake locations compiled since 1973. Details of the method used to determine this velocity structure can be found in a separate publication (Crosson, 1976a(Crosson, , 1976b …”