Work

Pre-seismic geomagnetic fusion anomaly extraction based on Spatially Weighted Non-negative Tensor Factorization

Year: 2026

Type: article

Abstract: . Earthquake preparation processes are known to generate geomagnetic anomalies, Existing methods for extracting pre-seismic geomagnetic anomalies from multi-station observations are limited by the lack of physically meaningful constraints. Considering that electromagnetic signal propagation is related to epicentral distance, we incorporate spatial relationships between observation stations and potential seismic source regions into non-negative tensor factorization (NTF), and propose a Spatially Weighted Non-negative Tensor Factorization (SW-NTF) method to extract fused pre-seismic geomagnetic anomalies from multi-station data. SW-NTF was applied to daily 1 Hz Z-component geomagnetic data recorded at seven stations from 90 days before to 30 days after the 2021 Ms 7.4 Madoi earthquake. Compared with traditional NTF, SW-NTF captures a more pronounced accelerated growth in the pre-seismic geomagnetic anomalies. The extracted anomalies exhibit two phases of S-shaped accelerated growth (day −85 to −60 and day −40 to −17). Spatially, anomalous signals initially appear at stations farther from the epicenter and progressively migrate toward the epicentral region as the earthquake approaches. The potential influence of space weather activity is examined, suggesting that the detected anomalies are not dominated by external geomagnetic disturbances. Temporal comparisons show that the two-phase acceleration of geomagnetic anomalies precedes similar acceleration in cumulative Benioff strain. Observed variation patterns are also consistent with magnetic field changes in rock loading experiments, and the spatiotemporal correspondence with b-values indicates that the anomalies likely reflect stress evolution in the crust during earthquake preparation.

Source: Natural hazards and earth system sciences

DOI: 10.5194/nhess-26-2151-2026