Emmy-Noether-Projekt "Brückenschlag zwischen Geodäsie und Seismologie"

Repeated large-magnitude earthquakes in a tectonically active, low-strain continental interior: the northern Tien Shan, Kyrgyzstan

Landgraf A., Dzhumabaeva A., Abdrakhmatov K.E., Strecker M. R., Macaulay E. A., Arrowsmith J. R., Sudhaus H., Preusser F., Rugel G. and Merchel S., (2016).

Journal of geophysical research, DOI: 10.1002/2015JB012714

wiley online library

 

Abstract

The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries.

To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismological investigations at two geomorphically distinct sites (Panfilovkoe and Rot Front) near the Kyrgyz capital Bishkek.

Although located near the historic epicenters, both sites were not affected by these earthquakes. Trenching was accompanied by dating stratigraphy and offset surfaces using luminescence, radiocarbon, and 10Be terrestrial cosmogenic nuclide methods.

At Rot Front, trenching of a small scarp did not reveal evidence for surface rupture during the last 5000 years. The scarp rather resembles an extensive debris-flow lobe.

At Panfilovkoe, we estimate a Late Pleistocene minimum slip rate of 0.2 ± 0.1 mm/a, averaged over at least two, probably three earthquake cycles. Dip-slip reverse motion along segmented, moderately steep faults resulted in hanging wall collapse scarps during different events.

The most recent earthquake occurred around 3.6 ± 1.3 kyr ago (1σ), with dip-slip offsets between 1.2 and 1.4 m. We calculate a probabilistic paleomagnitude to be between 6.7 and 7.2, which is in agreement with regional data from the Kyrgyz range.

The morphotectonic signals in the northern Tien Shan are a prime example of deformation in a tectonically active intracontinental mountain belt and as such can help understand the longer-term coevolution of topography and seismogenic processes in similar structural settings worldwide.

Geofon

SRCMOD - Database

    • Inversion modelling of geodetic (InSAR) and seismological data
    • earthquake slip complexity and co-seismic rupture history
    • Connecting earthquake models to observations
    • Kinematic earthquake source inversion

     

    In my research i am interested in how earthquakes ruptures behave and how and why earthquakes develop complex ruptures in space and time. Complex means that the earthquake ruptures e.g. across multiple fault planes with different geometries or slows down/accelerates in different areas. We know that earthquakes rupture with different degrees of complexity and we believe that larger earthquake rupture in more complex ways. This would however violate the common assumption of self-similarity of earthquakes across magnitudes. Often the choice of the modeled degree of complexity is however dependent on expert knowledge. Therefore i am looking for data driven ways to help us evaluate possibly rupture segmentation. Also I focus on small to medium sized earthquakes to investigate if we can resolve any complex ruptures from them or if they do not exhibit such behavior. I am using InSAR, GPS and seismological data.

    To asses the evolution of an earthquake rupture in time i have developed a multi-array backprojection code, which is available on github: Palantiri