|
|||||
|
|
Magnitude versus faults' surface parameters: quantitative relationships from the Aegean Region |
|
| Authors: | Spyros Pavlides Riccardo Caputo |
| Institution: | a Department of Geology and Physical Geography, Aristotle University of Thessaloniki, GR-54124, Thessaloniki, Greece b Di.S.G.G., University of Basilicata, Campus Macchia Romana, I-85100 Potenza, Italy |
| Abstract: | Historical and seismotectonic data from the broader Aegean Region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re-evaluated. All events associated to co-seismic surface faulting have been selected and further investigated, while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these ‘morphogenic earthquakes’ (sensu Bull. INQUA 16 (1993) 24]). In particular, in order to perform seismic hazard analyses, we compiled a list of all earthquakes where the surface rupture length (SRL), the maximum vertical displacement (MVD) or the average displacement (AD) is available. We thus obtained reliable values of these source parameters for 36 earthquakes, of which 26 occurred during the 20th century, 6 in the 19th century and the 3 remaining earlier. Magnitude versus SRL and MVD has been compiled for estimating empirical relationships. The calculated regression equations are: Ms=0.90·log(SRL)+5.48 and Ms=0.5·9log(MVD)+6.75, showing good correlation coefficients equal to 0.84 and 0.82, respectively. Co-seismic fault rupture lengths and especially maximum displacements in the Aegean Region have systematically lower values than the same parameters worldwide, but are similar to those of the Eastern Mediterranean–Middle East region. The envelopes of our diagrams are also calculated and discussed for estimating the worst-case scenario. Furthermore, for all investigated seismogenic structures, based on several geological criteria, we measured the ‘geological’ fault length (GFL), which is the total length of the neotectonic faults showing cumulative recent activity. We then compared SRL with GFL and their ratio shows a clear bimodal distribution with a major peak at 0.8–1.0, indicating that about 50% of the investigated earthquakes ruptured almost the entire fault length, while a second peak around the value of 0.5 is clearly related to a segmentation process of longer neotectonic structures. Further implications of this distribution are also discussed. Eventually, from the distribution of GFL versus magnitude we also infer an important geological threshold for the occurrence of ‘morphogenic earthquakes’ at about 5.5 degrees. |
| Keywords: | Author Keywords: Seismic hazard Morphogenic earthquakes Seismotectonics Surface rupture |
| 本文献已被 ScienceDirect 等数据库收录！ | |