T128 Multidisciplinary Studies of Fault System Deformation

Monday, 10 October 2011
1:30 PM - 5:30 PM
Room 200A-C

VERTICAL FAULT DISPLACEMENTS RESOLVED FROM PLEISTOCENE MARINE TERRACES, CRETE, GREECE: IMPLICATIONS FOR EARTHQUAKE HAZARDS AND TOPOGRAPHIC DEVELOPMENT OF THE HELLENIC MARGIN

Paper number: T128-14
Program: Technical Sessions
Time: 5:00 PM – 5:15 PM

Authors

Abstract

Most researchers agree that the Hellenic subduction zone (HSZ) represents a weakly-coupled plate interface unlikely to generate large earthquakes. Rather, faults responsible for destructive historic earthquakes are likely related to a series of prominent escarpments embedded in the forearc of the HSZ, suggesting a genetic link between seismic hazards and the building of topography. Discrepancies in current literature over the vertical kinematics (compressional vs. extensional) of faults responsible for relief across these escarpments impede the reliability of estimates of their seismic potential and their role in the topographic development of the Hellenic margin; information important to both seismic hazard and hydrocarbon resource potential in this and similar settings.

We utilize geomorphic and geochronologic datasets from Pleistocene marine terraces along the Asterousia escarpment (> 3700 m) of south-central Crete in order to reconcile competing models to assess uplift histories and vertical fault displacement amounts and rates. Flights of up to 6 terraces were mapped and elevations determined with DGPS at 15 sites along 75 km of coastline. 14C ages and correlation of terrace elevations with the global sea level curve indicate differential along strike rates of uplift and elucidate vertical motions along a potentially important fault over ~125 kyr.

We located and mapped a large normal fault cropping out on-shore near Tsoutsouros. Uplift rates for the Asteroussia footwall block are highest near the fault contact, decline westward, and have a mean value of ~1.0 mm/yr. The hanging wall exhibits mean uplift rates of ~0.3 mm/yr, suggesting ~0.7 mm/yr of late Pleistocene vertical fault motion. Our results imply that a large normal fault(s) bounds the Asteroussia mountain front and the genesis of large forearc escarpments and earthquake hazards are a consequence of extensional to transtensional processes at shallow crustal levels within the convergent HSZ.