HIGH VLF SIGNALS OBSERVATIONS OVER WESTERN US FAULTS BY DYNAMIC EXPLORER-2 SATELLITE

This work continues previous investigation on the problem of lithosphere-ionosphere coupling devoted to North Tyan-Shan and Baikal regions in the absence of seismic activity. The data from Dynamic Explorer-2 satellite were analyzed over the fault systems in the west part of US. These are results of electric field measurements by VEFI instrument in the bands 1-4 kHz, 4-16 kHz and 16-64 kHz and data on energetic particles from LAPI spectrometer. Digitized locations of the faults were taken from USGS database. We selected the orbits where electric field exceeds the upper decile. In band 1-4 kHz there were 37% of orbits, which satisfy this criterion, in band 4-16 kHz - 59%, in band 16-64 kHz 51% and in band 128-512 kHz - 54%. The locations of electric field jerks in different frequency bands usually do not coincide, though low and mid-latitude cases are located over certain faults. The best coincidence is observed in the band 16-64 kHz. In the central and southern part of US extremely large values (hundreds of mkV/m up to mV/m) of electric fields coincides with the underlaying faults, even if the peak is very narrow. Two regions have stable effect. The first one is bounded by the triangle formed by the Garlock fault zone (Western Garlock section) - San Andres fault zone (Mojave section) - Owens Valley fault zone (1822 Rupture section)(Fig.1). The second active zone is placed near Seattle, mainly in the vicinity of Straight Creek fault. On some orbits significant electron and ion fluxes were observed over the faults, in the zone of enhanced electric field (up to 0.1 ergs/cm^2/sec/ster) with energies up to 30 keV. The most intriguing fact is that these fluxes were preferably upward. The observed effect does not depend on magnetic activity and local time. Summary statistics and distributions are presented for all frequency bands.