17:15 〜 19:15
[SSS07-P18] The study of the evolution characteristics of the regional in-situ stress field in the Luzhou area of Sichuan Basin, China
★Invited Papers
キーワード：source mechanism, induced earthquake, regional and local stress field
With the ongoing expansion of shale gas development in the Sichuan Basin, both the scale and intensity of exploitation have increased, drawing increasing attention from both the scientific community and society regarding the issue of induced seismicity. Inverting the source mechanisms of induced earthquakes in this region and analyzing the evolution characteristics of regional and local stress fields is of significant practical importance for understanding the mechanisms of seismic initiation and managing the risks associated with induced seismicity. This study utilizes seismic waveform data from the Luzhou block, applying a joint inversion method of body and surface waves (CAP method) as well as the HASH method based on P-wave first motion and amplitude ratios. The source mechanisms of earthquakes with M ≧ 2.0 from 2016 to November 2023 in the Luzhou block were inverted, and stress tensors were derived from these mechanisms, providing a detailed structural stress field at varying magnitude levels and depths across the Luzhou region.
The results reveal that the reverse fault mechanism is the most prevalent in the Luzhou block, followed by the strike-slip mechanism, with normal faulting being the least common. For earthquakes with magnitudes greater than 3.0, reverse faulting dominates, followed by strike-slip faulting. For earthquakes in the 2.0–3.0 magnitude range, reverse faulting is again predominant, with strike-slip second and normal faulting the least observed. The stress characteristics and orientations of the principal stress axis at different depths in the Luzhou block vary. At both shallow and deep levels, the principal stress axis is oriented NW, with a reverse faulting stress nature, indicating the dominance of NW-directed horizontal compressive stress. In the fault disappearance zone, the principal stress axis is oriented NE, exhibiting more complex stress characteristics. Stress characteristics also exhibit variations across different magnitudes. For smaller earthquakes, the principal stress axis in the Luzhou block is oriented near EW and NW, particularly near the Huaying Mountain fault zone, where the axis is nearly horizontal, and the stress nature is reverse faulting. This is consistent with the stress state of the Huaying Mountain fault zone, which is primarily influenced by near-EW horizontal compressive stress. In the southern part of the Luzhou block, the principal stress axis is oriented NW, with reverse faulting as the dominant stress nature, aligning with the regional stress background. For larger magnitude earthquakes, the inverted stress field becomes more complex, especially in the northern segment of the Huaying Mountain fault zone, where the orientation of the stress axis is more intricate. In summary, seismic activity in the Luzhou block is predominantly compressive, consistent with the reverse faulting nature of the Huaying Mountain fault. Some earthquakes display shear characteristics, while smaller magnitude earthquakes (2.0–3.0) also exhibit extensional features.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 42474084).
The results reveal that the reverse fault mechanism is the most prevalent in the Luzhou block, followed by the strike-slip mechanism, with normal faulting being the least common. For earthquakes with magnitudes greater than 3.0, reverse faulting dominates, followed by strike-slip faulting. For earthquakes in the 2.0–3.0 magnitude range, reverse faulting is again predominant, with strike-slip second and normal faulting the least observed. The stress characteristics and orientations of the principal stress axis at different depths in the Luzhou block vary. At both shallow and deep levels, the principal stress axis is oriented NW, with a reverse faulting stress nature, indicating the dominance of NW-directed horizontal compressive stress. In the fault disappearance zone, the principal stress axis is oriented NE, exhibiting more complex stress characteristics. Stress characteristics also exhibit variations across different magnitudes. For smaller earthquakes, the principal stress axis in the Luzhou block is oriented near EW and NW, particularly near the Huaying Mountain fault zone, where the axis is nearly horizontal, and the stress nature is reverse faulting. This is consistent with the stress state of the Huaying Mountain fault zone, which is primarily influenced by near-EW horizontal compressive stress. In the southern part of the Luzhou block, the principal stress axis is oriented NW, with reverse faulting as the dominant stress nature, aligning with the regional stress background. For larger magnitude earthquakes, the inverted stress field becomes more complex, especially in the northern segment of the Huaying Mountain fault zone, where the orientation of the stress axis is more intricate. In summary, seismic activity in the Luzhou block is predominantly compressive, consistent with the reverse faulting nature of the Huaying Mountain fault. Some earthquakes display shear characteristics, while smaller magnitude earthquakes (2.0–3.0) also exhibit extensional features.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 42474084).