Stress and Strain Characteristics before the Mw 7.3 Maduo Earthquake and Its Implications for Future Earthquakes on the Maqin–Maqu Fault

Abstract

ABSTRACT To determine the crustal deformation and the stress–strain accumulation characteristics preceding the Mw 7.3 Maduo earthquake and the seismic potential of the Maqin–Maqu fault segment, the seismic data from small earthquake events and Global Positioning System (GPS) observations stations are collected. The b-value, the GPS velocity field, the GPS baseline, and the GPS strain parameters for multiple areas are calculated and analyzed. The results show a low b-value anomaly in the epicenter and its adjacent areas before the earthquake, which suggest that the stress level of the medium in this area was high before the earthquake. The regional GPS velocity field indicates that the earthquake epicenter is in an area where strain energy accumulates at varying slip rates and orientations. The deformation rates of the northeast-oriented baselines on the east side of the fault and the northwest-oriented baselines on the west side of the fault are lower than those observed near the three near north–south-oriented baselines, reflecting a small compressive deformation that occurred at the epicenter before the earthquake. Meanwhile, the motion of baselines QHYS-QHMD, QHYS-QHMQ, and QHGE-SCSP noticeably decreased, indicating that the area near the fault had already stored a great deal of strain energy prior to the earthquake. The rate of plane strain reduced in the epicenter region before the earthquake gradually since the second half of 2019, illustrating the deficit points to high stress conditions in the epicenter area. Furthermore, the area near the epicenter was characterized by high strain accumulation before the earthquake. The Maqin–Maqu segment of the East Kunlun fault is likely to be capable of generating strong earthquakes in the near future, because the current state of the area is similar to that of the Maduo epicenter before the onset of the earthquake.