Quaternary volcanism and segmented rupture of the Yilan-Yitong Fault Zone, NE China

Abstract

Although it has been speculated that the Quaternary volcanism may have affected the segmented rupture of active faults, the underlying mechanism remains unknown. The NE-trending, ∼700 km-long Yilan-Yitong Fault Zone (YYFZ), as the main branch of the Tancheng-Lujiang Fault Zone (TLFZ) in NE China, provides a very good laboratory to verify this hypothesis, given its distinct Quaternary volcanic eruptions and segmented late Quaternary activities. The previous study revealed that the Shulan segment of the YYFZ experienced intensive deformation during the Late Quaternary, whereas no surface evidence of tectonic deformation during the Late Quaternary was found in the Yitong segment, despite the greater intensity and spatial distribution of Quaternary volcanic eruptions along the latter. An interesting phenomenon is that the co-seismic surface ruptures of the active segments of the YYFZ “bypassed or terminated” from the Quaternary volcanoes. Thus, the Yitong and the Shulan segments of the YYFZ were selected here to further analyze the relationship between the Quaternary volcanism and segmented ruptures, based on high-resolution satellite image interpretation, large-scale geological and geomorphological mapping, magnetotelluric (MT) detection, trench excavation, and Quaternary chronological testing. The integrated data suggest that Quaternary volcanism influenced the strong earthquake rupture propagation process of the YYFZ. The MT data revealed the existence of hot magma chambers in the deeper part of the Yitong section, however, did not developed in the deeper part of the Shulan section. The underlying magma chambers may influence the rupture propagation process and segmentation of active faults by the mechanism of high-temperature bodies, the heterogeneity of fault structure and mechanical properties near the crater, and diffusion adjustment. This new observation is crucial both for the study of the Quaternary volcanism and segmented rupture of the active faults in NE China, and for the hazard assessment of strong earthquakes in similar tectonic settings worldwide.