Search

On 21 August 2017 at 20:57 (local time) a very shallow (H = 1.2 km), moderate (Md = 4.0), earthquake hit the volcanic island of Ischia (Southern Italy), causing the death of two people. The study of the damage to the buildings with the European Macroseismic Scale 98 (EMS-98), carried out immediately after the earthquake, highlighted that hilly area of Casamicciola Terme, on the northern side of the Mt. Epomeo, was the most damaged part of the island with locally quite relevant damage (I = VIII EMS). This seismic event is the first damaging earthquake in Ischia during the instrumental era. In fact, this provides, for the first time, the opportunity to integrate historical seismicity, macroseismic observations, instrumental information, and detailed mapping of the geological coseismic effects. In this work we evaluate the effects induced by the 2017 Casamicciola earthquake on the environment using the Environmental Seismic Intensity 2007 (ESI-07) macroseismic scale. This macroseismic analysis, together with the superficial coseismic faulting characteristics and the available geophysical information, allows us to reconsider the source model for the 2017 earthquake and the previous damaging historical earthquakes in the Casamicciola Terme area. The application of the ESI scale to the Casamicciola Terme earthquake of 21 August 2017 and the assignment of seismic intensity offers better spatial resolution, as well as an increase of the time window for the assessment of the seismic hazard, allowing to reduce the implicit uncertainty in the intensity attenuation laws in this peculiar volcano-tectonic setting. Since intensity is linked to the direct measure of damage, and it is commonly used in hazard assessment, we argue that building damage at Casamicciola Terme is strongly influenced by earthquake surface faulting and near field effects, and therefore controlled by the geometry of the seismic source.

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]

Before the arrival of the Spaniards in America, between the fourteenth and sixteenth centuries A.D., events and daily life were described through symbols in documents called codices. During the conquest, the Spaniards destroyed many of the codices because they were viewed as idolatrous. In Mexico and overseas there exist a number of codex that were artistically and consistently drawn by the Tlacuilo people who had strong knowledge in different disciplines, including natural processes, biodiversity, war, and social and religious problems. These codices contain five kinds of glyphs: numerals, calendrical, pictographic, ideographic and phonetic. One codex that contains an especially large amount of information about natural processes such as climate, volcanic eruptions, and major earthquakes, is the Telleriano Remensis. A careful analysis of this codex and related documents provides evidence for 12 earthquakes defined in space and time. Earthquakes were represented by two combined symbols: motion and earth. These symbols are not related to earthquakes themselves, but together, represent a seismic event, whose effects could be related to intensities of V in the ESI 2007 scale. The effects interpreted in the codex (tilted buildings, rolling stones, landslides, and human migration) suggest that earthquake strengths are very similar to those described in the 2007 ESI scale. The Mexicas, influenced by the Mayan culture, assigned a determined number of bars (tlalli) to each earthquake giving them a numerical representation and scale. This indicates that prehispanic cultures, such as the Aztec (Mexicas), Mixtec and Zapotec, already had some assessment criteria to scale earthquakes and their effects. [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]

On 21 August 2017 at 20:57 (local time) a very shallow (H = 1.2 km), moderate (Md = 4.0), earthquake hit the volcanic island of Ischia (Southern Italy), causing the death of two people. The study of the damage to the buildings with the European Macroseismic Scale 98 (EMS-98), carried out immediately after the earthquake, highlighted that hilly area of Casamicciola Terme, on the northern side of the Mt. Epomeo, was the most damaged part of the island with locally quite relevant damage (I = VIII EMS). This seismic event is the first damaging earthquake in Ischia during the instrumental era. In fact, this provides, for the first time, the opportunity to integrate historical seismicity, macroseismic observations, instrumental information, and detailed mapping of the geological coseismic effects. In this work we evaluate the effects induced by the 2017 Casamicciola earthquake on the environment using the Environmental Seismic Intensity 2007 (ESI-07) macroseismic scale. This macroseismic analysis, together with the superficial coseismic faulting characteristics and the available geophysical information, allows us to reconsider the source model for the 2017 earthquake and the previous damaging historical earthquakes in the Casamicciola Terme area. The application of the ESI scale to the Casamicciola Terme earthquake of 21 August 2017 and the assignment of seismic intensity offers better spatial resolution, as well as an increase of the time window for the assessment of the seismic hazard, allowing to reduce the implicit uncertainty in the intensity attenuation laws in this peculiar volcano-tectonic setting. Since intensity is linked to the direct measure of damage, and it is commonly used in hazard assessment, we argue that building damage at Casamicciola Terme is strongly influenced by earthquake surface faulting and near field effects, and therefore controlled by the geometry of the seismic source. [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]