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Geological Constraints on the Seismic Activity of the Mid-section of the Minjiang Fault in the Eastern Margin of the Tibet Plateau

Description: 

The Minjiang Fault, located in the western boundary of the Minshan active block, is situated above a large-scale, east-dipping electrical structure boundary zone. The upward flow of the Songpan-Ganzi lower-crust low-resistivity layer beneath the Minshan active block provides an important driving force for the frequent large earthquakes along the Minjiang Fault. In this study, we constrained the seismic activity of the mid-section of the Minjiang Fault through a detailed analysis of three paleoseismic trenches and the dating of samples. Our study found that at the Gusicun section, the occurrence ages of three paleoearthquake events (EG3, EG2, and EG1) are estimated to be 10827-4034 aBP, 3907-2023 aBP, and 1945-685 aBP, respectively. At the Lajichang section, the occurrence ages of the EL3, EL2, and EL1 events are 6159-5820 aBP, 3904-2305 aBP, and 2139-300 aBP, respectively. In addition, the Luoshigou trench’s most recent event (ES1) occurred in 3258-1171 aBP. By using the incremental dating method, the ages of the three paleoearthquake events (E3, E2, and E1) along the fault are estimated to be 6158-5829 aBP, 3283-2292 aBP, and 1980-1130 aBP, respectively. The elapsed time since the most recent event is estimated to be 2021-1201 aBP. Using the OxCal software, the average earthquake recurrence period of the fault is estimated to be 2218±262 years (μ±2σ), with a variation coefficient of 0.64.

According to the study, no fresh surface/near-surface rupture corresponding to the Diexi earthquake was found in the mid-section of the Minjiang Fault, and the dating results of the most recent earthquake event do not match the Diexi earthquake. Therefore, the Diexi earthquake is not closely related to the mid-section of the Minjiang Fault. Due to the recent occurrence of a major earthquake close to the recurrence interval, combined with the seismic activity characteristics around the Minshan active block, it is necessary to pay attention to the future seismic hazard of the Minjiang Fault.

Session: Learning Across Geological, Geophysical & Model-Derived Observations to Constrain Earthquake Behavior [Poster Session]

Type: Poster

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Zhujun

Student Presenter: No

Invited Presentation: 

Authors