New results of tomographic processing of surface and body wave data provided some evidence of str... more New results of tomographic processing of surface and body wave data provided some evidence of structural differences in crust-mantle transition between northern and southern part of the Apulian plate, playing an important role in the geodynamic evolution of the Central Mediterranean. In order to support the inferences derived from tomographic data and to better constrain the lateral limits of these heterogeneities, Bouguer anomalies, available in the area, based on data supplied by the Italian Petrol Agency (AGIP), were processed and interpreted through a 2D1/2 density modelling. In the southern part of the Apulian plate, the obtained results suggest the presence, with respect to the northern part, of a thinner typical crust combined with a thicker transition zone having a slightly lower density than the more typical mantle material. The northern Apulian structure either has a transition zone of marginal properties or no transition zone at all with a crust-mantle passage relatively ...
Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in t... more Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robu...
Computational Science and Its Applications – ICCSA 2020, 2020
The historical seismicity catalogs report that the Gargano area (Apulia region, southern Italy) h... more The historical seismicity catalogs report that the Gargano area (Apulia region, southern Italy) has been site of medium to high magnitude earthquakes. Instrumental seismicity suffers of the poor coverage of the seismic stations of the RSN (National Seismic Network). To improve the seismological monitoring of the area, in 2013 the OTRIONS seismic network (OSN), managed by the University of Bari - Italy, in cooperation with INGV (National Institute of Geophysics and Volcanology), was installed. In this study, focal mechanisms of single and composite events have been computed using 118 micro-earthquakes occurred in this area. We subdivided the dataset into subsets according to their location and depth, distinguishing between the Promontory zone and the Apulian foredeep. High quality focal mechanisms and low-misfit stress tensor inversion were obtained for three groups of events. To better constrain the stress tensor we included also focal mechanism solutions obtained in previous studies. In the southwestern Apulian foredeep zone, a normal fault kinematics is inferred, normal to the Apennine stress direction; in the Promontory zone, the fault kinematics indicate inverse fault mechanisms striking in NE-SW direction. Differently from previous analyses, the stress orientations inferred in this study agree with those inferred in the World Stress Map.
In previous papers surface dispersion data have been combined with the results of deep seismic re... more In previous papers surface dispersion data have been combined with the results of deep seismic refraction data to derive a regionalization of the lithosphere-asthenosphere system and to investigate the presence of significant heterogeneity down to depths of 350 km along two profiles in the North European Fennoscandian area; a regionalized upper mantle model for the whole area down to more than 400 km is given as cross sections. We have extended that approach to North America. The older part of the shield shows lid thickness up to more than 100 km with, if any, weak shear velocity contrast to the underlying layer. The surrounding areas are characterized by a thinner lid; a stronger low-velocity zone to lid contrast may be found in peripheral areas. A map of the lithosphere-asthenosphere system has been derived, permitting a better regional resolution of the shear-wave velocity distribution with depth beneath different regions of North America. The correlation between the lithosphere-...
Bulletin of the Seismological Society of America, 2003
ABSTRACT The need for effective strategies for preventing and mitigating damage caused by earthqu... more ABSTRACT The need for effective strategies for preventing and mitigating damage caused by earthquake-induced landslides has stimulated recent developments of tech-niques for the assessment of seismic-landslide exposure at a regional scale. However, for a rational risk management, a crucial element is represented by the time horizon of the hazardous events. A new way to incorporate the time factor in seismic-landslide hazard assessment is proposed here. It consists of evaluating the temporal recurrence of seismically induced slope failure conditions inferred from the Newmark's model: First, by adopting Arias Intensity to quantify seismic shaking, well-established meth-ods of seismic hazard assessment are employed to obtain the occurrence probabilities for different levels of seismic shaking in a time interval of interest. Then, some empirical relations, based on the Newmark's model, are employed to evaluate the slope critical acceleration a c for which a prefixed probability exists that seismic shaking would result in landslide triggering. The obtained a c values represent the minimum slope resistance required to keep the probability of seismic-landslide trig-gering within the prefixed value. Therefore, the space distribution of the calculated a c values can be promptly compared with the actual in situ a c values of specific slopes to estimate whether these slopes have a significant probability of failing under seismic action in the future. An example of this approach, applied to an area in southern Italy (Daunia region), shows that the introduction of the time factor signifi-cantly modifies the representation of the spatial hazard and allows evaluation of the relevance of seismicity as a landslide triggering agent.
Physics of the Earth and Planetary Interiors, 2004
The presence of a structural heterogeneity between the northern part of the Adriatic plate (Centr... more The presence of a structural heterogeneity between the northern part of the Adriatic plate (Central Mediterranean) and its southernmost sector was hypothesised by different authors and also confirmed recently by 3D velocity models obtained through surface wave tomography and local earthquake tomography. However, the seismological data leave some uncertainty about the location of the lateral limits of this heterogeneity and
Northern Apulia is an emerged portion of the Adriatic microplate, representing the foreland–fored... more Northern Apulia is an emerged portion of the Adriatic microplate, representing the foreland–foredeep area of a stretch of the Apennine chain in southern Italy. The interaction between the relatively rigid microplate and the contiguous more deformable domains is responsible for the intense seismicity affecting the chain area. However strong, sometimes even disastrous, earthquakes have also hit northern Apulia on several
New results of tomographic processing of surface and body wave data provided some evidence of str... more New results of tomographic processing of surface and body wave data provided some evidence of structural differences in crust-mantle transition between northern and southern part of the Apulian plate, playing an important role in the geodynamic evolution of the Central Mediterranean. In order to support the inferences derived from tomographic data and to better constrain the lateral limits of these heterogeneities, Bouguer anomalies, available in the area, based on data supplied by the Italian Petrol Agency (AGIP), were processed and interpreted through a 2D1/2 density modelling. In the southern part of the Apulian plate, the obtained results suggest the presence, with respect to the northern part, of a thinner typical crust combined with a thicker transition zone having a slightly lower density than the more typical mantle material. The northern Apulian structure either has a transition zone of marginal properties or no transition zone at all with a crust-mantle passage relatively ...
Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in t... more Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robu...
Computational Science and Its Applications – ICCSA 2020, 2020
The historical seismicity catalogs report that the Gargano area (Apulia region, southern Italy) h... more The historical seismicity catalogs report that the Gargano area (Apulia region, southern Italy) has been site of medium to high magnitude earthquakes. Instrumental seismicity suffers of the poor coverage of the seismic stations of the RSN (National Seismic Network). To improve the seismological monitoring of the area, in 2013 the OTRIONS seismic network (OSN), managed by the University of Bari - Italy, in cooperation with INGV (National Institute of Geophysics and Volcanology), was installed. In this study, focal mechanisms of single and composite events have been computed using 118 micro-earthquakes occurred in this area. We subdivided the dataset into subsets according to their location and depth, distinguishing between the Promontory zone and the Apulian foredeep. High quality focal mechanisms and low-misfit stress tensor inversion were obtained for three groups of events. To better constrain the stress tensor we included also focal mechanism solutions obtained in previous studies. In the southwestern Apulian foredeep zone, a normal fault kinematics is inferred, normal to the Apennine stress direction; in the Promontory zone, the fault kinematics indicate inverse fault mechanisms striking in NE-SW direction. Differently from previous analyses, the stress orientations inferred in this study agree with those inferred in the World Stress Map.
In previous papers surface dispersion data have been combined with the results of deep seismic re... more In previous papers surface dispersion data have been combined with the results of deep seismic refraction data to derive a regionalization of the lithosphere-asthenosphere system and to investigate the presence of significant heterogeneity down to depths of 350 km along two profiles in the North European Fennoscandian area; a regionalized upper mantle model for the whole area down to more than 400 km is given as cross sections. We have extended that approach to North America. The older part of the shield shows lid thickness up to more than 100 km with, if any, weak shear velocity contrast to the underlying layer. The surrounding areas are characterized by a thinner lid; a stronger low-velocity zone to lid contrast may be found in peripheral areas. A map of the lithosphere-asthenosphere system has been derived, permitting a better regional resolution of the shear-wave velocity distribution with depth beneath different regions of North America. The correlation between the lithosphere-...
Bulletin of the Seismological Society of America, 2003
ABSTRACT The need for effective strategies for preventing and mitigating damage caused by earthqu... more ABSTRACT The need for effective strategies for preventing and mitigating damage caused by earthquake-induced landslides has stimulated recent developments of tech-niques for the assessment of seismic-landslide exposure at a regional scale. However, for a rational risk management, a crucial element is represented by the time horizon of the hazardous events. A new way to incorporate the time factor in seismic-landslide hazard assessment is proposed here. It consists of evaluating the temporal recurrence of seismically induced slope failure conditions inferred from the Newmark's model: First, by adopting Arias Intensity to quantify seismic shaking, well-established meth-ods of seismic hazard assessment are employed to obtain the occurrence probabilities for different levels of seismic shaking in a time interval of interest. Then, some empirical relations, based on the Newmark's model, are employed to evaluate the slope critical acceleration a c for which a prefixed probability exists that seismic shaking would result in landslide triggering. The obtained a c values represent the minimum slope resistance required to keep the probability of seismic-landslide trig-gering within the prefixed value. Therefore, the space distribution of the calculated a c values can be promptly compared with the actual in situ a c values of specific slopes to estimate whether these slopes have a significant probability of failing under seismic action in the future. An example of this approach, applied to an area in southern Italy (Daunia region), shows that the introduction of the time factor signifi-cantly modifies the representation of the spatial hazard and allows evaluation of the relevance of seismicity as a landslide triggering agent.
Physics of the Earth and Planetary Interiors, 2004
The presence of a structural heterogeneity between the northern part of the Adriatic plate (Centr... more The presence of a structural heterogeneity between the northern part of the Adriatic plate (Central Mediterranean) and its southernmost sector was hypothesised by different authors and also confirmed recently by 3D velocity models obtained through surface wave tomography and local earthquake tomography. However, the seismological data leave some uncertainty about the location of the lateral limits of this heterogeneity and
Northern Apulia is an emerged portion of the Adriatic microplate, representing the foreland–fored... more Northern Apulia is an emerged portion of the Adriatic microplate, representing the foreland–foredeep area of a stretch of the Apennine chain in southern Italy. The interaction between the relatively rigid microplate and the contiguous more deformable domains is responsible for the intense seismicity affecting the chain area. However strong, sometimes even disastrous, earthquakes have also hit northern Apulia on several
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