Discussion on the magnitude or intensity limitation of paleoearthquake events

Abstract

The magnitude is an important parameter that characterizes the size of earthquakes. However, in paleoearthquake studies, it is difficult to precisely determine the rupture parameters closely related to seismic moment, making it challenging to directly calculate the magnitude of events. Researchers often assume that event sequences consist of characteristic earthquakes with similar magnitudes or use empirical relationships based on known magnitudes of historical earthquakes to estimate magnitudes. However, previous studies have shown that the assumption of characteristic earthquakes is overly simplistic, and magnitude estimation based on empirical relationships is limited by various errors. Therefore, there is a pressing need to explore new methods to improve the reliability of magnitude assessments for ancient earthquake events. In recent years, the successful application of three-dimensional combination trenches has demonstrated that these trenches contain rich deformation information about events, confirming the feasibility of assessing event sizes within trenches. Using the example of the Copper Mine trench on the Altyn Tagh fault, this article utilizes the deformation intensity revealed within the trench, including vertical displacement, deformation zone width, and total tensile strain, to estimate the scale of the event sequence. Data analysis results indicate that the deformation intensity parameters have a certain positive correlation with the relative magnitude, and there is also some correlation among these parameters. Therefore, the information on deformation intensity within the trench can be used to assess the relative magnitude of events, and fully exploring the deformation information within trenches can provide valuable insights and references for the reasonable evaluation of the magnitude of paleoearthquake events. This underscores the importance of considering such information in paleoearthquake research.

Keywords

• magnitude limitation
• paleoearthquake events
• empirical relationships
• deformation intensity
• copper mine trench