New geodetic constraints on strain accumulation along the North Anatolian Fault from the Karliova Triple Junction to the N Aegean Trough
Wednesday, 17 December 2014: 5:45 PM
We use the MIT E Mediterranean GPS velocity field and InSAR observations to constrain DEFNODE block models to investigate rates of strain accumulation for the North Anatolian Fault (NAF) system. The new observations define well a SW splay at ~36.8°E and bifurcation into S and N branches E of the Marmara Sea (~31.5°E). The GPS observations provide good spatial coverage of central Anatolia and are consistent with highly coherent plate motion for the eastern, central, and northwestern parts of the plate from the Karliova Triple Junction to S of the Sea of Marmara. Significant strain is observed along the northern part of Anatolia S of the NAF, indicating increasing rates of motion from E to W reaching 2-3 mm/yr integrated along the length of the fault (i.e., ~10% of the NAF slip rate). Non-linear post-seismic effects from the 1999 Izmit/Düzce earthquake sequence that are evident up to seven years after the events may contribute to the observed strain, although postseismic effects were corrected for in the time series; more detailed studies are continuing and will be reported. The overall strain rate of the Marmara Sea block is dominantly N-S extension, consistent with that expected for a right-step on a right-lateral fault. Our preferred block model constrained by GPS has increasing slip rates from E to W from 22-24 mm/yr along the E to E-central segment to 27-28 mm/yr along the W segment, in good agreement with our InSAR estimates using ENVISAT and ERS data. E of the “central bend” (~35°E) the Fault is under extension (1-4 mm/yr) and to the W, compression (0-6 mm/yr). Right-lateral slip rates from our preferred fault-wide model (i.e. highly simplified) are 23-24 mm/yr on the Izmit Bay segment, 17-18 mm/yr on the NW striking Princes’ Islands segment (likely including slip on faults in the Çınarcık Basin), and 23-24 mm/yr on the E-W striking Central Marmara Fault and Ganos segments. The S NAF branch has consistent modeled slip rates of 4-5 mm/yr along its full extent.