Regional-Scale, Natural Persistent Scatterer Interferometry, Island of Crete (Greece), and Comparison to Vertical Surface Deformation on the Millennial-, and Million-Year Time-Scales

Kurzfassung

This thesis explores the suitability of Persistent-Scatterer Interferometry (PSI) for the first time on a regional scale to answer current research questions in active tectonics and earthquake geology. PSI is a widely-used satellite-geodetic technique, which traditionally has been applied to urban areas on the 5-km scale, profiting from densely-spaced anthropogenic scatterers. Here, I used radar interferometry data from the ERS satellites to monitor the surface deformation over the time period from 1992 to 2000. The island of Crete represents an ideal study area, because it represents an over 250 km-wide, aerially exposed forearc high located above the Hellenic subduction zone. The purpose of this thesis is to determine the pattern of surface deformation on different spatial and temporal scales, ranging from currently active deformation to the past vertical deformation preserved in the landscape. I analyzed Persistent Scatterer Interferometry (PSI) data to detect the active vertical surface-deformation pattern across Crete. Results of the PSI analysis illustrate that the western Crete is strongly affected by uplift, central Crete is relatively stable, and eastern Crete is dominated by subsidence. This deformation pattern is consistent with activity on offshore upper-crustal faults. Furthermore, the PSI map pattern shows abundant small-scale strain gradients, particularly in central and eastern Crete, which coincide with the topographic expression of active normal faults, implying that the natural PSI technique applied here is suitable to detect regional-scale surface deformation on varying scales. The PSI signal across some of the normal faults indicates reverse-sense vertical motion, implying transient behaviour or aseismic creep along the upper-crustal faults on Crete. For the detection of the vertical surface-deformation pattern on the millennial and the million-year time-scale, I synthesized and analysed river profiles, uplifted paleo-shorelines, and Neogene sedimentary rocks. All, the resultant Holocene and Pleistocene uplift rates, and the geomorphological analysis yield a heterogeneous pattern of vertical surface deformation across Crete, consistent with crustal-scale segmentation and the PSI analysis. The results of this thesis indicate that the vertical surface-deformation pattern across Crete is heterogeneous on the decadal-, the millennial-, and the million-year time-scale. This may imply that the Hellenic subduction zone is not the main tectonic structure to produce the surface-deformation pattern observed on Crete, but instead upper-crustal faults are responsible for the present and past vertical deformation. These faults are also capable producing large and devastating earthquakes and will need to be considered in seismic hazard assessment and mitigation studies. Long-term constraints on the active deformation pattern provided by geological measurements are an important data source, in particular in the absence of effective kinematic and mechanical faulting models.