GEOMETRY OF THE 1954 FAIRVIEW PEAK-DIXIE VALLEY EARTHQUAKE SEQUENCE FROM A JOINT INVERSION OF LEVELING AND TRIANGULATION DATA

In 1954, four earthquakes greater than M(S) = 6.0 occurred within a 30 -km radius and in a period of 6 months. Elevation and angle changes ca lculated from repeated leveling and triangulation surveys which span t he coseismic period provide constraints on the fault geometries and co seismic slip of the faults which were activated. The quality of the co seismic geodetic data is assessed. Corrections are applied to the leve ling data for subsidence due to groundwater withdrawal in the Fallen a rea, and a rod miscalibration error of 150 +/- 30 ppm is isolated in l eveling surveys made in 1967. The leveling and triangulation observati ons are then simultaneously inverted using the single value decomposit ion (SVD) inversion method to determine fault geometries and coseismic slip. Using SVD, it is possible to determine on which faults slip is resolvable given the data distribution. The faults are found to dip be tween 50 degrees and 80 degrees and extend to depths of 5 to 14 km. Th e geodetically derived slip values are generally equal to, or greater than, the maximum observed displacement along the surface scarps. Wher e slip is resolvable the geodetic data indicates the 1954 sequence con tained a significant component of right-lateral slip. This is consiste nt with the N15 degrees W trending shear zone which geodetic surveys h ave detected in western Nevada.