Liquefaction case histories and empirical relations of earthquake magnitude versus distance from the broader Aegean region

In this study, historical and seismotectonic data from the broader Aegean region, which are relevant to liquefaction phenomena, have been collected in order to investigate the relationship between epicentral (Re) and fault (Rf) distance versus magnitude. Initially, a preliminary catalogue of sites where liquefaction induced ground failures or structural damages is presented. These liquefaction case histories have been triggered by 88 earthquakes since 1509. Based on these data, an upper bound of maximum epicentral distance (Remax) for a given earthquake magnitude Ms is calculated. The corresponding equation is Ms = 4.742 + 4.655 × 10−3Remax + 0.8907 log(Remax). This curve fits well with those proposed by previous studies and shows that the epicentral distance increases along with increasing magnitude. The lower limit of earthquake magnitude that induced liquefaction within the study area is Ms = 5.0, while the upper limit is Ms = 7.6. Furthermore, the closest distance of the liquefied sites to the causative faults was estimated in order to determine a distance-magnitude relation and to give numerical results for seismic hazard assessment. The calculated regression that is suggested is: Ms = 5.224 + 7.34 × 10−3Rfmax + 0.488 log(Rfmax) for 5.5 ≤ Ms ≤ 7.1 and it concerns normal faulting data. The strike-slip faulting data were few and the attempt to estimate regression for this category of faulting was unsuccessful. Moreover, the distribution of data reported to the instrumental era (after 1900) indicates that there is a rise in the values of the epicentral distance of liquefied sites triggered by earthquakes of magnitudes Ms > 6.6. The equation of the best-fit curve based on these data is: Ms = 0.01Re + 6.463 ± 0.46. In addition, an attempt was made to calculate regressions of Re on Ms, according the focal mechanism of the event. In what concerns the normal faulting data, the equation of the best-fit curve and the upper bound curve are Ms = 0.01Re + 6.38 ± 0.38 and Ms = 0.021Remax + 5.3, respectively, for Ms values between 5.5 and 7.1.