Characteristic slip distribution and earthquake recurrence along the eastern Altyn Tagh fault revealed by high-resolution topographic data

Abstract

AbstractThe seismic cycle model is roughly constrained by limited offset data sets from the eastern Altyn Tagh fault with a low slip rate. The recent availability of high-resolution topographic data from the eastern Altyn Tagh fault provides an opportunity to obtain distinctly improved quantitative, dense measurements of fault offsets. In this paper, we used airborne light detection and ranging data and unmanned aircraft vehicle photogrammetry to evaluate fault offsets. To better constrain the large earthquake recurrence model, we acquired dense data sets of fault displacements using the LaDiCaoz_v2.1 software. A total of 321 offset measurements below 30 m highlight two new observations: (1) surface-slip of the most recent earthquake and multiple events exhibit both short-wavelength (m-scale) and long-wavelength (km-scale) variability; and (2) synthesis of offset frequency analysis and coefficient of variation indicate regular slip events with ∼6 m slip increment on fault segments to the west of the Shulehe triple junction. The distribution of offsets and paleoseismological data reveal that the eastern Altyn Tagh fault exhibits characteristic slip behavior, with the characteristic slip of ∼6 m and a recurrence period ranging from 1170 to 3790 years. Paleoearthquake recurrence intervals and slip increments yield mean horizontal slip-rate estimates of 2.1–2.6 mm/yr for fault segments to the west of the Shulehe triple junction. Assuming a 10 km rupture depth and a 30 GPa shear modulus, we estimated a characteristic slip event moment magnitude (Mw) of ∼7.6. Finally, we discuss the interaction mechanism between Altyn Tagh fault (strike fault) and the NW-trending thrust faults (reverse faults) that caused the sudden decrease of sinistral slip rate at the Shulehe and Subei triple junctions; our results support the eastward “lateral slip extrusion” model.