Papanikolaou, Ioannis; (2003) Generation of high-resolution seismic hazard maps through integration of earthquake geology, fault mechanics theory and GIS techniques in extensional tectonic settings. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Throw-rate data constrained by offset geological surfaces of known age have been collected in order to construct a new type of high-resolution seismic hazard map and test the hypothesis that historical seismicity (c. 1000yrs) can adequately represent the recurrence of earthquakes on geological timescales (104-105). Analyses of deformation rate data in the central and southern Apennines indicate that faults are interacting and form a soft-linked normal fault array about 158 km and 175 km in length respectively. Centrally located faults exhibit higher throw-rates than distal faults implying that seismic hazard varies accordingly along strike of both arrays. Summed throw-rates on faults imply maximum extension rates of 3.9 ± 0.8 mm/yr across the central Apennines and 1.1 ± 0.25 mm/yr across the southern Apennines. In the southern Apennines finite throw data were also collected and compared with present day deformation rates, demonstrating that fault interaction started very early (20-30%) in the deformation story. Two independent methods of obtaining deformation rate data have been used (measured values from displaced post-glacial sediments in the central and southern Apennines and predicted values from an equation that predicts extensional deformation rates over long time periods). These deformation rate data are converted into earthquake frequencies using established empirical relationships, turned into seismic hazard maps and attenuated accordingly with the bedrock geology using a new technique developed during this study. Hazard maps from both areas are considerably different from existing seismic hazard maps and demonstrate that hazard distribution varies significantly over short distances due to fault throw-rate variations along strike or changes in bedrock geology. Recurrence intervals extracted from the maps are averaged over 18 kyrs, a time span that encompasses many earthquake cycles, eliminating both the incompleteness as well as the temporal clustering problems associated with the historical earthquake records. These recurrence intervals combined with the historical record are used to calculate conditional probabilities of earthquake shaking at certain intensity values. The construction of these hazard maps implies that in several normal faulting environments, geological fault slip-rate data supported by local geological site-response data and GIS techniques, can offer higher spatial resolution and more reliable representation of seismic hazard than maps based on historical seismicity.

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