Testing Models of Earthquake Cycle Deformation Using Geodetic Observations Along the North Anatolian Fault
Hussain, Ekbal; Wright, T.J.; Walters, R.J.; Houseman, G.A.; Yamasaki, T.
University of Leeds, UNITED KINGDOM
The North Anatolian Fault is a major continental right lateral strike-slip system located in northern Turkey. The fault slips with an average rate of 20-30 mm/yr and is the main focus of deformation on the northern edge of the Anatolia region as it moves westwards towards the Hellenic subduction zone. The fault has accommodated 12 large earthquakes (M6.7 and above) since 1939 with a dominant westward progression in seismicity. These past ruptures provide us with a unique window into different stages of the earthquake cycle along the same strike-slip system. By analysing strain accumulation for different parts of the fault we aim to test whether deformation reaches a steady state or whether it varies continuously throughout the earthquake cycle. Interferometric Synthetic Aperture Radar (InSAR) is now a fairly well established technique for measuring interseismic deformation. In this presentation, we will firstly compare the StaMPS and Pi-RATE InSAR time series processing techniques for a single track covering the 1999 Izmit rupture. We will then show results from several locations along the fault, including the location of the 1939 Erzincan rupture, a M7.9 earthquake that started the 20th Century earthquake sequence. We finally combine the InSAR results with published GPS data to determine a velocity field map for the region that is consistent with both data sets, and determine variations in interseismic strain accumulation rates and locking depth along the Fault. By creating profiles of the spatial variation in strain we are able to test the assumption that these regions are at different stages of the earthquake cycle. Most current models of earthquake cycle deformation match either the focused strain observed during the interseismic period or the rapid post-seismic deformation signal in the few years following an event, but are unable to account for both. We test new models for the whole earthquake cycle that include a lower-crustal weak zone using our geodetic observations from the North Anatolian Fault.