Observing of pre-earthquake transients features in the Earth atmosphere-ionosphere environment associated with M6.4 and M7.1 Ridgecrest, California, Earthquakes of July 2019

We are presenting a preliminary study on the multi-parameter analysts of transient phenomena observed in the Earth atmosphere-ionosphere environment plausibly associated with M6.4 of July 4, 2019, and M7.1 of July 6, 2019, in Ridgecrest California, the largest and earthquakes in California for last 20 years. We are collecting operational data from four instruments which were recorded hourly and daily: 1. Radon level variations (two gamma stations in Southern CA); 2. Very Low Frequency (VLF) modulated signals in the frequency range 10-50 kHz from several VLF/LF transmitters 3. Outgoing long-wavelength radiation (OLR obtained from NPOES) on the top of the atmosphere (TOA), and 4. Weather Data -Temperature, Atm. Pressure and Relative humidity. We also analyzed the Atmospheric chemical potential (ACP) obtained from NASA assimilation models and electron density variations in the ionosphere via GPS Total Electron Content (GPS/TEC). NOAA satellite thermal observation shows an increase of infrared radiation observed which was associated with the acceleration of OLR observed from polar orbit satellites reaching a maximum near the epicenter on June 24. The VLF signal received at Orange, CA was strongly disturbed on all tracks on June 22, and the perturbations in the signal were also observed on June 25 and on July 6. The epicenter near Ridgecrest, CA, is situated about 220 kilometers NE of the two-radon monitoring stations in Orange and Palm Springs. Real-time hourly data show an increase on both sensors on July 1 (3 days before the M6.4 of July 4, 2019). Those increases in radon coincide) with an increase in the atmospheric chemical potential (on July 1) measured near the epicentral area from satellite data. The GPS/Total Electron Content data indicated an increase of electron concentration in ionosphere on July 1st and 2nd, 1-2 days before the M6.4 Earthquake.

Although the radon sensors were far from both epicentral area, we observed from ground and satellite instruments anomalous trend before the earthquake ground and satellite starting 12 days before the M6.4 and continuously up to the M7.1 of July 6, 2019. We examined the possible correlation between different pre-earthquake signals in the frame of a multidisciplinary investigation of the Lithosphere -Atmosphere -Ionosphere coupling concept.