Abstract
Quantifying the structure and kinematics of active faults is the key to understanding the India-Eurasia continental collision. While the boundary faults of blocks in the southeastern Tibetan Plateau region have been under scrutiny for decades, relatively less attention has been paid to the active faults within the blocks. Here, we use structural, sedimentary, and geomorphic characteristics to constrain the late Quaternary kinematics and slip rates of the Nantinghe fault, a major fault within the southeastern Tibetan Plateau region. The Nantinghe fault is an active, dominantly left-lateral strike-slip fault that can be traced continuously for 500 km. We analyze the late Quaternary slip rates at five sites along the fault trace. The latest Quaternary apparent throw rates are typically less than 1 mm/a. The rate of strike-slip displacement is estimated to be an order of magnitude higher, 4.0 ± 0.6 (2σ) mm/a. Trenching suggests that active fault behavior is dominated by strike-slip faulting and reveals five earthquake events with refined information of timing in the last 5,000 years, suggesting an averaged recurrence interval of ∼1,000 a. These observations agree with GPS-derived estimates and show that late Quaternary slip rates on the Nantinghe fault are comparable to those on other major active strike-slip faults in the southeastern Tibetan Plateau. The newly-obtained slip rates on the Nantinghe fault, integrated with previous estimates on other faults in this region, provide direct evidence that favors the continuum models over the rigid block ones, on the Quaternary deformation mechanism in the India-Asia continental collision.
Highlights
The Indian-Asian continental collision during the past ca. 50 Myr has induced crustal deformation in a vast region that extends more than 2,000 km from the Himalaya Mountains to Central and East Asia (Molnar and Tapponnier, 1975; Royden et al, 2008; Taylor and Yin, 2009)
When these two schools of view are applied to eastern Asia, large slip rates on major faults are required by the block models, but not by the continuum models
The Nantinghe fault, with its 3.5–5.4 mm/a millennial slip rate, is located in a swath of the largest slip rate on the velocity profile by Shi et al (2018b). This swath, containing the Daying, Ruili, Wanding, and Nantinghe faults on the surface, is located between two localized, NE-SW-trending channels of low-velocity anomalies at the mid-crustal depths from a high-resolution shearwave seismic tomography model of this region (Bao et al, 2015), (Figure 13B). All these results indicate that the Red River fault does not dominate the present-day kinematics of the Indochina Block, and the continuum models could play a more dominant role in the Quaternary tectonics of this region
Summary
The Indian-Asian continental collision during the past ca. 50 Myr has induced crustal deformation in a vast region that extends more than 2,000 km from the Himalaya Mountains to Central and East Asia (Molnar and Tapponnier, 1975; Royden et al, 2008; Taylor and Yin, 2009). The Nantinghe Fault deformation is regionally distributed in the shallow brittle crust, and is essentially continuous at depth (Molnar and Tapponnier, 1975; England and McKenzie, 1982; England and Houseman, 1986; Clark and Royden, 2000) When these two schools of view are applied to eastern Asia, large slip rates on major faults are required by the block models, but not by the continuum models. In the continuum models, the Red River fault forms a striking geomorphic feature, it does not dominate the present-day kinematics of the whole block, and the slip rates of the internal faults may be comparable with, or even greater than, that of the Red River fault (Copley, 2008). Because of their obvious geomorphic features, fast slip rates, and the occurrence of devastating earthquakes, the block-bounding
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