Southern California Permanent GPS Geodetic Array: Continuous measurements of regional crustal deformation between the 1992 Landers and 1994 Northridge earthquakes

Abstract

Abstract. The southern California Permanent GPS Geodetic Array (PGGA) was established in 1990 across the Pacific-North America plate boundary to continuously monitor crustal deformation. We describe the development of the array and the time series of daily positions estimated for its first 10 sites in the 19-month period between the June 28, 1992 (Mw=7.3), Landers and January 17, 1994 (Mw=6.7), Northridge earthquakes. We compare displacement rates at four site locations with those reported by Feigl et al. [1993], which were derived from an independent set of Global Positioning System (GPS) and very long baseline interferometry (VLBI) measurements collected over nearly a decade prior to the Landers earthquake. The velocity differences for three sites 65-100 km from the earthquake's epicenter are of order of 3-5 mm/yr and are systematically coupled with the corresponding directions of coseismic displacement. The fourth site, 300 km from the epicenter, shows no significant velocity difference. These observations suggest large-scale postseismic deformation with a relaxation time of at least 800 days. The statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets; two possible noise models fit the PGGA data equally well as described in the companion paper by Zhang et al. [this issue]; the pre-Landers data are too sparse and heterogeneous to derive a reliable noise model. Under a fractal white noise model for the PGGA data we find that the velocity differences for all three sites are statistically different at the 99% significance level. A white noise plus flicker noise model results in significance levels of only 94%, 43%, and 88%. Additional investigations of the pre-Landers data, and analysis of longer spans of PGGA data, could have an important effect on the significance of these results and will be addressed in future work.

Continuous GPS Observations of Postseismic Deformation Following the 16 October 1999 Hector Mine, California, Earthquake (Mw 7.1)

“…Following the 1992 Landers sequence, several modes of transient postseismic deformation are thought to have occurred, as described extensively by Shen et al (1994), Massonnet et al (1996), Peltzer et al (1996Peltzer et al ( , 1998, Bock et al (1997), Savage and Svarc (1997), Deng et al (1998), and Pollitz et al (2000). It is therefore reasonable to expect that some similar modes of postseismic deformation might be present in the time series presented here.…”

Noise in multivariate GPS position time-series

“…The correlations between different components do not seem to be significant. Insignificant correlations between components has also been shown by Bock et al (1997).…”

Pre-seismic strain anomalies and coseismic deformation of Meinong earthquake from continuous GPS

“…The data from dense continuous GPS array provide us to estimate fault-slip rates, infer fault geometry, and assess regional seismic hazard (e.g., Bock et al 1997;Sagiya et al 2000;Lin et al 2010). Taiwan is situated at an active collision boundary, in which numerous folds and thrust belts formed due to the convergence between the Luzon arc and the Chinese continental margin.…”