Growth of Geological Structure & Topography

The relationship between individual earthquakes and the longer-term growth of topography and of geological structures is not fully understood, but is key to our ability to make use of topographic and geological data sets in the contexts of seismic hazard and wider-scale tectonics. Using observations of an earthquake at the edge of the Tarim Basin, Eleanor Ainscoe at the University of Oxford investigated the active fold-and-thrust belt using seismic waveforms and interferometric synthetic aperture radar as part of her D.Phil thesis.

Her earthquake mechanism and location correspond closely to a fault mapped independently by seismic reflection, indicating that the earthquake was on a preexisting ramp fault over a depth range of ∼9–13 km. However, the geometry of folding in the overlying fluvial terraces cannot be fully explained by repeated coseismic slip in events such as the 2015 earthquake nor by the early postseismic motion shown in her interferograms; a key role in growth of the topography must be played by other mechanisms.
This study was recently published in the Journal of Geophysical Research.

Seismic reflection profile. Dashed black lines: fault planes found by our uniform slip models. H’ and H: fold axes. N2-Q: Pliocene-Quaternary 3.6 Ma to present. N2: Pliocene. N1: Miocene. E: Paleogene. Pz-Mz: Paleozoic-Mesozoic. Pre-Pz: Precambrian. (left) Colored squares show the depth distribution of moment release per unit depth in our finite slip model.

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