The possible statistical relation of Pc1 pulsations to Earthquake occurrence at low latitudes

Abstract

Abstract. We examine the association between earthquakes and Pc1 pulsations observed at a low-latitude station in Parkfield, California. The period under examination is ∼7.5 years in total, from February 1999 to July 2006, and we use an automatic identification algorithm to extract information on Pc1 pulsations from the magnetometer data. These pulsations are then statistically correlated to earthquakes from the USGS NEIC catalog within a radius of 200 km around the magnetometer, and M>3.0. Results indicate that there is an enhanced occurrence probability of Pc1 pulsations ∼5-15 days in advance of the earthquakes, during the daytime. We quantify the statistical significance and show that such an enhancement is unlikely to have occurred due to chance alone. We then examine the effect of declustering our earthquake catalog, and show that even though significance decreases, there is still a statistically significant daytime enhancement prior to the earthquakes. Finally, we select only daytime Pc1 pulsations as the fiducial time of our analysis, and show that earthquakes are ∼3-5 times more likely to occur in the week following these pulsations, than normal. Comparing these results to other events, it is preliminarily shown that the normal earthquake probability is unaffected by geomagnetic activity, or a random event sequence.

Additional attenuation of natural VLF electromagnetic waves observed by the DEMETER spacecraft resulting from preseismic activity

“…These perturbations have been observed both using ground-based measurements and satellites. They are believed to occur over a wide range of frequencies, from direct current to very high frequency [Larkina et al, 1989;Tate and Daily, 1989;Serebryakova et al, 1992;Molchanov et al, 1993;Parrot, 1994aParrot, , 1994bAsada et al, 2001;Hattori, 2004;Hobara and Parrot, 2005;Bortnik et al, 2008;Němec et al, 2008Němec et al, , 2009Píša et al, 2012]. Nevertheless, it is very difficult to identify these effects in the ionosphere, because the amplitude of the earthquake-related perturbations is much lower than the amplitude of natural variations due to other sources.…”

Ionospheric precursors for crustal earthquakes in Italy

“…Although many mechanisms for the earthquake precursor occurrence have been proposed (see a special issue by Hayakawa et al, 2006, for recent progress in this area), the researchers are still far from the understanding of these relationships. For instance, a thorough analysis of the association between earthquakes and Pc1 pulsations (Bortnik et al, 2008) has revealed an enhanced occurrence probability of Pc1 pulsations 5-15 days in advance of the earthquakes, during the daytime. This relationship was shown to be statistically significant.…”

Decrease of intensity of ELF/VLF waves observed in the upper ionosphere close to earthquakes: A statistical study

“…Among other reported precursors (changes in temperature and concentration, resistivity changes, etc. ), electromagnetic perturbations possibly connected with seismic activity have been recently discussed by several authors, both using ground‐based [ Tate and Daily , 1989; Asada et al , 2001; Bortnik et al , 2008] and satellite data [ Parrot and Mogilevsky , 1989; Larkina et al , 1989; Molchanov et al , 1993; Parrot , 1994; Hobara et al , 2005; Molchanov et al , 2006; Němec et al , 2008]. The reported electromagnetic effects span over the large range of frequencies (from DC up to visible light), timescales (from several minutes up to a few months) and may be of various nature (enhancement of wave intensity, attenuation of wave intensity, modification of wave characteristics).…”