Swarm Satellite Magnetic Field Data Analysis Prior to 2019 Mw = 7.1 Ridgecrest (California, USA) Earthquake

Dedalo Marchetti,Angelo De Santis,Gianfranco Cianchini,Martina Orlando,Saioa A Campuzano,Loredana Perrone,Alessandro Piscini,Maurizio Soldani,Dario Sabbagh

doi:10.3390/geosciences10120502

Dedalo Marchetti, Angelo De Santis + Show 7 more

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https://doi.org/10.3390/geosciences10120502

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Abstract

This work presents an analysis of the ESA Swarm satellite magnetic data preceding the Mw = 7.1 California Ridgecrest earthquake that occurred on 6 July 2019. In detail, we show the main results of a procedure that investigates the track-by-track residual of the magnetic field data acquired by the Swarm constellation from 1000 days before the event and inside the Dobrovolsky’s area. To exclude global geomagnetic perturbations, we select the data considering only quiet geomagnetic field time, defined by thresholds on Dst and ap geomagnetic indices, and we repeat the same analysis in two comparison areas at the same geomagnetic latitude of the Ridgecrest earthquake epicentre not affected by significant seismicity and in the same period here investigated. As the main result, we find some increases of the anomalies in the Y (East) component of the magnetic field starting from about 500 days before the earthquake. Comparing such anomalies with those in the validation areas, it seems that the geomagnetic activity over California from 222 to 168 days before the mainshock could be produced by the preparation phase of the seismic event. This anticipation time is compatible with the Rikitake empirical law, recently confirmed from Swarm satellite data. Furthermore, the Swarm Bravo satellite, i.e., that one at highest orbit, passed above the epicentral area 15 min before the earthquake and detected an anomaly mainly in the Y component. These analyses applied to the Ridgecrest earthquake not only intend to better understand the physical processes behind the preparation phase of the medium-large earthquakes in the world, but also demonstrate the usefulness of a satellite constellation to monitor the ionospheric activity and, in the future, to possibly make reliable earthquake forecasting.

Highlights

On 6 July 2019, at 03:19:53 UTC, an Mw = 7.1 earthquake happened in Southern California, Ridgecrest (35.770◦ N, 117.599◦ W), at a depth of 8.0 km
We focus our attention on the Ridgecrest earthquake that occurred on 6 July 2019 and the possible electromagnetic anomalies detected by Swarm satellites during the preparation phase of the earthquake
Such that at 14 local time, in the epicentral area, some anomalies (4 over 10) have been detected 500 days an increase of anomalies is considered as possibly related to the preparatory phase of the California before the event, but for the US East Coast, 3 anomalies have been detected 2 h before, proposing this

Summary

Introduction

A Worldwide Statistical Correlation (WSC) analysis was applied on 4.7 years of Swarm magnetic field and electron density data, finding a significant correlation of concentrations of ionospheric anomalies with the worldwide shallow M5.5+ earthquakes in the same period [15] They found that the largest concentrations of anomalies precede large earthquakes, with each anticipation time increasing with the magnitude of the seismic event, confirming the Rikitake law [16] for electromagnetic pre-earthquake anomalies from satellite data. We focus our attention on the Ridgecrest earthquake that occurred on 6 July 2019 and the possible electromagnetic anomalies detected by Swarm satellites during the preparation phase of the earthquake This represents an extension of a recent paper [19] that analysed different physical quantities in the lithosphere, atmosphere and ionosphere, but here we are focusing especially on the magnetic field data of the Swarm mission.

Data and Methods

Results

The same

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Discussion and Conclusions