HR: 0800h
AN: T51B-1346    [Abstracts]
TI: Thermal Infrared ASTER Observations of Faults in Southern California
AU: * Eneva, M
EM: meneva@san.rr.com
AF: Imageair Inc., 10513 Caminito Westchester, San Diego, CA 92126 United States
AB: Reports on earthquake precursors observed in the thermal infrared (TIR) data from several satellites have caused mixed reactions. Some researchers have identified precursory anomalies, such as increased temperatures of several degrees over several days in areas extending up to hundreds of kilometers. In view of the uncertainties in the data, others have been skeptical that such changes can be reliably and uniquely associated with seismic events. This problem is a subset of the more general question how to interpret TIR observations from space for the purpose of fault characterization. Although faults are often clearly discernable in thermal images, the contributions of various factors to any temporal variability in their thermal properties are not clear. These factors include vegetation, soil moisture, surface and air temperature, atmospheric water vapor, and perhaps even wind. Extracting anomalies specifically associated with earthquakes in view of this natural variability and in the presence of observational uncertainties is a difficult task at best. Using standard higher-level TIR products (e.g., surface temperature) derived from radiance at sensor is likely questionable without additional corrections. We address these questions through the analysis of 60 km x 60 km images collected by the ASTER instrument on board of the Terra satellite. ASTER is unique in that five of its 14 channels are TIR, with a spatial resolution of 90 m (compared with at least 1-km spatial resolution of instruments used in previous reports of precursory anomalies). We focus on a specific area in southern California (32.8⁰N - 34.5⁰N, 115.9⁰W - 117.2⁰W) that includes substantial parts of the San Andreas, San Jacinto and Elsinore faults, as well as two recent M5.2 and M4.9 earthquakes (June 12 and 16, 2005). In addition to the existing ASTER data, mostly collected in the daytime, we have made arrangements for future data collections over the next year, with emphasis on nighttime TIR data that will be more suitable for the intended study. It is expected that the analysis of this unique time series of TIR images will help us to place limits on the observed and natural variability of the thermal properties of faults. Understanding these limits is a prerequisite in the search for any thermal anomalies.
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 5134 Thermal properties
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8040 Remote sensing
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Tectonophysics [T]
MN: Fall Meeting 2005