Statistical Assessment of Magnetic Precursors to the April ۱, ۲۰۱۴ Chile ۸.۲ Earthquake Using Swarm Satellite Data

Satellite-based monitoring of geomagnetic field variations offers a promising avenue for identifying earthquake precursors. The use of satellite data to detect such anomalies has garnered significant attention, given its global coverage and independence from ground-based limitations. In this study, we applied the characteristic curve method to Swarm satellite magnetic data to investigate pre-seismic anomalies preceding the Mw ۸.۲ Chile earthquake on April ۱, ۲۰۱۴. After subtracting the International Geomagnetic Reference Field (IGRF-۱۴), we identified a statistically significant anomaly in the northward magnetic component (BN) approximately ۳۳ days before the event. The characteristic curve method, which is based on plotting the satellite data over the study area repeatedly on consecutive orbits, enabled quantification of this deviation, revealing a statistically significant signal while accounting for natural geomagnetic variability. Graphical analysis of the data highlighted this anomaly as a pronounced feature, distinguishable from typical fluctuations. This anomaly exceeded ±۲۰ nT uncertainty bounds and persisted across multiple orbits. To validate its uniqueness, we analyzed two control intervals, three months before and after the study window, using the same method, confirming that no comparable anomalies occurred outside the precursor period. The anomaly’s directional specificity, temporal isolation, and amplitude support its interpretation as a genuine pre-seismic signal, likely linked to lithosphere-atmosphere-ionosphere coupling processes. These findings demonstrate the robustness of the characteristic curve method for satellite data and reinforce the potential of Swarm observations in short-term earthquake forecasting.

کلیدواژه ها:

Characteristic curve method ، Chile earthquake ، geomagnetic anomaly ، precursor detection ، SWARM satellite