Pino, Nicola Alessandro

Distance scaling of earthquake-induced ground motion is studied in the Erzincan region, located in the eastern part of the North Anatolian Fault zone. The data set used in this study consists of 170 aftershocks of the MS ! 6.8 Erzincan earthquake of 13 March 1992, with moment magnitudes between 1.5 and 4.0. In order to empirically obtain the scaling relationships for the high-frequency S-wave motion, regressions are carried out on 352 horizontal-component short-period seismograms, all recorded within a hypocentral distance of 40 km, to empirically obtain the scaling relationships for the high-frequency S-wave motion. Peak ground velocities are measured in selected narrow-frequency bands, in the frequency range of 1.0–16.0 Hz, and are subsequently regressed to define a piecewise linear attenuation function, a set of excitation terms, and a set of site terms. Results are modeled in the framework of random vibration theory, using a bilinear geometrical spreading function, g(r), characterized by a crossover distance at 25 km: g(r)!r"1.1 is used for r ! 25 km, whereas g(r)!r"0.5 is used for larger distances. An extremely low-quality factor, Q(f ) ! 40(f /f ref)0.45, is used to describe the anelastic crustal attenuation in the region, consistently with the independent results of Akinci and Eyidogan (1996, 2000). Excitation terms are well matched by using a Brune spectral model with stress drop Dr ! 10 MPa (taken from the recent literature, Grosser et al., 1998). An effective high-frequency, distance-independent rolloff spectral parameter, jeff ! 0.02 sec, is obtained in this study. Peak ground acceleration predictions based on these parameters show a much more rapid decrease with distance than the relations usually used in Turkey, indicating that our results should only be applied to the Erzincan region itself.

Volcanoes reawakening after long repose must rupture the crust before magma can erupt. Rupture is preceded by repeatable variations in the rate of seismicity with ground movement, which trace the amount of applied stress that is released by local earthquakes. A rupturing sequence has been developing across four episodes of ground uplift at Italy’s Campi Flegrei caldera: in 1950-1952, 1969-1972, 1982-1984 and since 2004. We predicted in 2016 that the approach to rupture would continue after an additional uplift of 30-40 cm at the location of largest movement. We have updated our analysis with new data on changes in the numbers of local earthquakes with amounts of ground movement. Here we show that subsequent events have confirmed our prediction and that the unrest has been changing the structure of Campi Flegrei’s crust. The results provide new constraints for evaluating the volcano’s potential to erupt or to subside without eruption.

The use of modern broadband seismometers allows the observation of dynamic and static near-field effects. In the fortunate case of the great 1994 Bolivia earthquake a 6 mm coseismic permanent offset was observed at distances of about 600 km. On the other hand no surface static displacement from moderate events has been observed yet. This is mainly due to the intrinsic difficulties in the instrument removal. In the present paper we analyze broadband waveforms from a couple of events in southern Italy, recorded at distance of 50 km, by applying the technique for instrument removal recently introduced by Zhu [2003]. We derive stable and reliable measures of very small coseismic static offset produced by moderate magnitude earthquakes. Our results, successfully tested against synthetic prediction, give permanent displacement of a few tenths of millimeters, one order of magnitude smaller than usual geodetic resolution.

In the modern society of risk (Beck, 1986), risk reduction education projects and awareness campaigns play a central and relevant role. The last twenty-five years have witnessed a flourishing of studies, research projects, educational experiments and actions to reduce natural risks. Our principal experiences in risk reduction activities, gained in over fifteen years, concerned: - EDURISK, an educational project for risk reduction addressed to schools and teachers. Explicit objective of EDURISK is to promote risk awareness and the active role of citizens in its reduction; therefore, a goal of social change (AA.VV., Pessina and Camassi eds, 2012); - education and psychosocial activities realized with students, teachers and citizens in the post emergencies of L’Aquila in the 2009 (Crescimbene et al. 2010; Moretti et al. 2011) and in the Po Plain earthquake in the 2012 (La Longa, 2013); - training activity for the Civil Protection volunteers involved in the “Io non Rischio” campaign (Postiglione et al., 2016). One of the most relevant problems of all these activities for risk reduction is the assessment process (La Longa, 2008). To have the tools and be able to consider the right variables to understand if the activities put in place produced desired outcomes. We arrived to the conclusion that the process knowledge-awareness-action never occur automatically, within an educational process, but this process must be accompanied in the direction of doing. To facilitate this process, it is necessary to understand better what are the elements and factors that influence it. In this sense, the data collected in recent years, on risk perception may represent good basis to identify the key-points to active the process knowledge-awareness-action. We think that improve risk perception of common people is the first goal to reach to be able to mitigate and reduce seismic risk. In this direction since the year 2013, we built the Seismic Risk Perception Questionnaire (SRP-Q) to investigate risk perception in the Italian citizens. In the last three years we collected over 9,000 questionnaires by web (www.terremototest.it) and in the year 2015 we conducted a Computer Assisted Telephone interview (CATI) on a national statistical sample of over 4,000 people. Our method consists of identify principal variables that influence risk perception scores and use it to design risk reduction activities. We executed an explorative factor analysis (FA) on the seismic risk perception data. These datasets derived by the CATI Survey conducted on an Italian statistical sample (N= 4012) in the first months of 2015. Results of the FA describe for each indicator, considered in the SRP-Q (Crescimbene et al. 2013), some components that explain variability among scores observed and correlated variables, in terms of a potentially lower number of variables called factors. Considering the principal components of each indicator (Hazard, Exposure, Vulnerability, People and Community), we described these components and obtained useful indications to design activities that may improve seismic risk perception. By this method, we think to realize an educational design able to valorise those factors that promote social change for risk reduction. In the near future, we will apply on small groups the training program and the activities and will evaluate if the risk perception scores will be improved.

On October 31, 2002 a ML=5.4 earthquake occurred in southern Italy, at the margin between the Apenninic thrust belt (to the west) and the Adriatic plate (to the east). In this area, neither historical event nor seismogenic fault is reported in the literature. In spite of its moderate magnitude, the earthquake caused severe damage in cities close to the epicenter and 27 people, out of a total of 29 casualties, were killed by the collapse of a primary school in S. Giuliano di Puglia. By inverting broadband regional waveforms, we computed moment tensor solutions for 15 events, as small as ML=3.5 (Mw=3.7). The obtained focal mechanisms show pure strike-slip geometry, mainly with focal planes oriented to NS (sinistral) and EW (dextral). In several solutions focal planes are rotated counterclockwise, in particular for later events, occurring west of the mainshock. From the relocated aftershock distribution, we found that the mainshock ruptured along an EW plane, and the fault mechanisms of some aftershocks were not consistent with the mainshock fault plane. The observed stress field, resulting from the stress tensor inversion, shows a maximum principal stress axis with an east–west trend (N83°W), whereas the minimum stress direction is almost N–S. Considering both the aftershock distribution and moment tensor solutions, it appears that several pre-existing faults were activated rather than a single planar fault associated with the mainshock. The finite fault analysis shows a very simple slip distribution with a slow rupture velocity of 1.1 km/s, that could explain the occurrence of a second mainshock about 30 h after. Finally, we attempt to interpret how the Molise sequence is related to the normal faulting system to the west (along the Apennines) and the dextral strike-slip Mattinata fault to the east.

Post-seismic relaxation is known to occur after large or moderate earthquakes, on time scales ranging from days to years or even decades. In general, long-term deformation following seismic events has been detected by means of standard geodetic measurements, although seismic instruments are only used to estimate short timescale transient processes. Albeit inertial seismic sensors are also sensitive to rotation around their sensitive axes, the recording of very slow inclination of the ground surface at their standard output channels is practically impossible, because of their design characteristics. However, modern force-balance, broad- band seismometers provide the possibility to detect and measure slow surface inclination, through the analysis of the mass position signal. This output channel represents the integral of the broad-band velocity and is generally considered only for state-of-health diagnostics. In fact, the analysis of mass position data recorded at the time of the 2009 April 6, L’Aquila (MW = 6.3) earthquake, by a closely located STS-2 seismometer, evidenced the occurrence of a very low frequency signal, starting right at the time of the seismic event. This waveform is only visible on the horizontal components and is not related to the usual drift coupled with the temperature changes. This analysis suggests that the observed signal is to be ascribed to slowly developing ground inclination at the station site, caused by post-seismic relaxation following the main shock. The observed tilt reached 1.7 × 10−5 rad in about 2 months. This estimate is in very good agreement with the geodetic observations, giving comparable tilt magnitude and direction at the same site. This study represents the first seismic analysis ever for the mass position signal, suggesting useful applications for usually neglected data.

Destructive earthquakes are rare in France yet pose a sizable seismic hazard, especially when critical infrastructures are concerned. Only a few destructive events have occurred within the instrumental period, the most important being the 11 June 1909, Lambesc (Provence) earthquake. With a magnitude estimated at 6.2 [Rothé, 1942], the event was recorded by 30 observatories and produced intensity IX effects in the epicentral area, ~30 km north of Marseille. We collected 30 seismograms, leveling data and earthquake intensities to assess the magnitude and possibly the focal mechanism of this event. Following this multidisciplinary approach, we propose a source model where all relevant parameters are constrained by at least two of the input datasets. Our reappraisal of the seismological data yielded Mw 5.8-6.1 (6.0 preferred) and Ms 6.0, consistent with the magnitude from intensity data (Me 5.8) and with constraints derived from modeling of coseismic elevation changes. Hence, we found the Lambesc earthquake to have been somewhat smaller than previously reported. Our datasets also constrain the geometry and kinematics of faulting, suggesting that the earthquake was generated by reverse-right lateral slip on a WNW-striking, steeply north-dipping fault beneath the western part of the Trévaresse fold. This result suggests that the fold, located in front of the Lubéron thrust, plays a significant role in the region’s recent tectonic evolution. The sense of slip obtained for the 1909 rupture also agrees with the regional stress field obtained from earthquake focal mechanisms and microtectonic data as well as recent GPS data.

One of the challenges on disasters’ understanding is the assessment of impact from a more global perspective, adding to their scenario of injuries, deaths, homeless and economic losses, those effects that are mostly widespread and could last for a long period of time, driving to a serious disruption of a community or a society. Seismic disasters are not just the results of the energy released by the earthquake or buildings’ vulnerability: social, demographic, cultural parameters may instead play a crucial, yet underestimated, role. We carried out a pilot study to investigate the demographic perspective of the impact of 1968 Belice and 1980 Irpinia-Basilicata earthquakes on local communities. The macroseismic MCS intensities were used as a primary parameter upon which the demographic scenario was derived. Population annual growth rates, the ageing index, the child-woman ratio, and the Gini index from the demographic data census of the period 1951-2011 were analyzed to assess population dynamics, age structure evolution and its level of spatial concentration within the disasters’ areas. Demographic data were then matched to macroseismic intensities to outline a new, original analysis which describes the impact of the two seismic disasters with a broad multi-parameter perspective. The results highlight also the existence of a general marginality of most affected areas with respect to the processes of population growth, ageing and fertility, as well as for distribution of the regional population, occurring already before the disasters stroke. This marginality might have enhanced the impact of disasters by significantly increasing vulnerability.

Seismic recordings are immediately available when an earthquake occurs. Their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques, which usually need some tests to provide robust results. However, immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation. Very simple analysis may provide useful information, giving insight in source complexity. Right after the 6 April 2009 L'Aquila earthquake (MW = 6.3), we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. The fracture occurred in two stages, with initial updip propagation, successively proceeding toward SE, possibly on a different plane. We also analyzed the strongest aftershock (MW = 5.6), showing that useful indications could be retrieved for lower magnitude events.

To understand the source complexity of the April 6, 2009 L’Aquila earthquake (MW = 6.3), a quick seismological analysis is done on the waveforms of the mainshock and the larger aftershock that occurred on April 7, 2009. We prove that a simple waveform analysis gives useful insights into the source complexity, as soon as the seismograms are available after the earthquake occurrence, whereas the reconstruction of the rupture dynamics through the application of sophisticated techniques requires a definitely longer time. We analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. We found that two distinct rupture patches associated with different fracture propagation directions and possibly occurring on distinct rupture planes, characterized the source kinematics of the April 6 events. An initial updip propagation successively proceeds toward SE, possibly on a different plane. We also show that the same processing, applied to the April 7, 2009 aftershock (MW = 5.6), allows us to obtain useful information also in the case of lower magnitude events. Smaller events with similar location and source mechanism as the mainshock, to be used as Green’s empirical function, occur in the days before or within tens of minutes to a few hours after the mainshock. These quick, preliminary analyses can provide useful constraints for more refined studies, such as inversion of data for imaging the rupture evolution and the slip distribution on the fault plane. We suggest implementing these analyses for real, automatic or semi-automatic, investigations.