Crustal deformation of Long Valley Caldera, eastern California, inferred from L-band InSAR

Akiko Tanaka(1)

(1) Geological Survey of Japan, AIST, AIST Tsukuba Central 7, 1-1-1 Higashi, 305-8567, Tsukuba, Japan


Since mid-1980, Long Valley Caldera has been intensely monitored for volcanic and tectonic activity. This monitoring effort has revealed a wide spectrum of geophysical processes. In 1980, a strong earthquake swarm struck the southern margin of Long Valley Caldera, marking the onset of the current period of volcanic unrest. This unrest included recurring swarms of moderate earthquakes, including four M>6 events, and uplift of the resurgent dome within the caldera which totals approximately 80 cm. Periods of significant deformation and seismicity followed in 1983, 1989- 1990, 1996, and 1997-1998. After a sharp increase in the deformation rate during the summer to autumn of 1997, the caldera was relatively inactive, with no significant deformation since the spring of 1998 [e.g., Langbein 2003].

Previous studies showed that InSAR images of Long Valley Caldera reveal a pattern of surface deformation that resembles that expected from analysis of ground-based geodetic data [e.g., Thatcher and Massonnet, 1997; Fialko et al., 2001; Tizzani et al., 2007; Hooper and Zebker, 2007]. They used InSAR data of ERS-1/2 acquired on a sub-yearly interval from 1992 to 2000.

SAR interferometric analyses using JERS-1 and ALOS/PALSAR images of Long Valley Caldera are performed. JERS-1 interferogram (June 1993-August 1998) shows a small region of subsidence associated the Casa Diablo geothermal power plant, which is superimposed on a broad scale uplift/expansion of the resurgent dome. PALSAR interferograms show no deformation of the resurgent dome, as expected. However, it may show a small region of subsidence associated the Casa Diablo geothermal power plant.



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