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We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1−6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1−4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2−9.1 m Myr−1 with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows/liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research.

The Environmental Seismic Intensity (ESI) scale has been officially released in 2007 and is based on the quantification of Earthquake Environmental Effects. Due to its quantitative nature, the scale improves the process of assessing macroseismic intensities, particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective. Following a large number of publications that applied this relatively newly established scale, there is some need for parametrization. This is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales. This study has three main goals. Firstly, to enrich and compile an ESI 2007 database from earthquakes in Greece by adding 4 new events. Secondly, to extract a relationship between Magnitude and the ESI 2007 for Greece and the Mediterranean. Thirdly, to offer a preliminary estimate of how the intensity attenuates with distance, after developing a code in Python language to assist this process. The ESI 2007 scale was applied in the 1995 Ms = 6.6 Kozani-Grevena earthquake, the 1978 Mw = 6.5 Thessaloniki earthquake, the historic 1894 Atalanti earthquake sequence (M = 6.4 and M = 6.8) and the 365AD event in Crete (M = 8.4). These events were selected because they have well documented and extensive co-seismic effects, including primary and secondary surface ruptures, rockfalls, landslides and liquefaction phenomena. For the Kozani earthquake, extracted results were correlated with SAR interferograms, in order to provide a complete and high spatial resolution of the ground deformation. Both the Kozani-Grevena and the Thessaloniki events produced a maximum intensity IX on the ESI 2007 scale, the Atalanti earthquake produced a maximum intensity X and the 365AD Crete earthquake a maximum intensity XII. Overall, the ESI 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the Kozani-Grevena epicentral area where due to the poor quality of buildings, existing scales overestimated the intensity by one degree compared to the ESI 2007. It is interesting to note that both for Greece and the Mediterranean area a strong correlation exists between Mw and the ESI 2007 scale. In particular, the following relationships between the Mw and the ESI scale have been extracted: i) for Greece I o(ESI 2007) = 3.1427 exp (0.1643Mw) and ii) for the Mediterranean I o(ESI 2007) = 3.3543exp (0.1557Mw). However, more events and more data regarding the intensity distributions are required to establish the intensity attenuation with distance. [ABSTRACT FROM AUTHOR]

The early 2014 Cephalonia (Ionian Sea, western Greece) earthquake sequence comprised two main shocks with almost the same magnitude (Mw 6.0) occurring successively in short time (January 26 and February 3) and space (western Cephalonia, Paliki peninsula). Two different almost parallel NE-SW striking and SE dipping at a steep-angle dextral strike-slip fault zones with small reverse component corresponded to the two events and were activated onland in Paliki. Many earthquake environmental effects (EEE) were induced by both earthquakes in Paliki offering the possibility to apply the ESI 2007 scale. They are classified into primary and secondary effects. Primary effects comprise uplift, subsidence and surface ruptures. Secondary effects include ground cracks, slope movements, liquefaction and hydrological anomalies. The VIII intensities are assigned to sites of maximum uplift in the central-eastern part of Paliki. The VII intensities are assigned to sites with maximum subsidence, surface ruptures and large-volume slope movements in the eastern coastal zone of Paliki, the northern part of Paliki and the northern part of Argostoli peninsula, respectively. The VI intensities are assigned to sites with ground cracks and slope movements mainly in the northern part of Paliki and the western part of Aenos Mt, respectively. The lowest V intensities are observed in the southern part of Paliki associated with small-volume slope movements. From the comparison of all data, it is concluded that there is a strong correlation between the active faults, the displacement discontinuities detected from already published interferometric analysis and the spatial distribution of the EEE. [ABSTRACT FROM AUTHOR]

We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1–6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1–4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2–9.1 m Myr−1 with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows/liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research. [ABSTRACT FROM AUTHOR]