Papers by Enrico Serpelloni
Tectonophysics, 2006
The Iberian Peninsula and the Maghreb experience moderate earthquake activity and oblique, ∼ NW-S... more The Iberian Peninsula and the Maghreb experience moderate earthquake activity and oblique, ∼ NW-SE convergence between Africa and Eurasia at a rate of ∼ 5 mm/yr. Coeval extension in the Alboran Basin and a N35°E trending band of active, left-lateral shear deformation in the Alboran-Betic region are not straightforward to understand in the context of regional shortening, and evidence complexity of deformation at the plate contact. We estimate 86 seismic moment tensors (M W 3.3 to 6.9) from time domain inversion of near-regional waveforms in an intermediate period band. Those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors. The solutions associated to the Trans-Alboran shear zone show predominantly strike-slip faulting, and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction (σ 1 at N350°E). At the N-Algerian and SW-Iberian margins, reverse faulting solutions dominate, corresponding to N350°E and N310°E compression, respectively. Over most of the Betic range and intraplate Iberia, we observe predominately normal faulting, and WSW-ENE extension (σ 3 at N240°E). From GPS observations we estimate that more than 3 mm/yr of African (Nubian)-Eurasian plate convergence are currently accommodated at the N-Algerian margin, ∼ 2 mm/yr in the Moroccan Atlas, and ∼ 2 mm/yr at the SW-Iberian margin. 2 mm/yr is a reasonable estimate for convergence within the Alboran region, while Alboran extension can be quantified as ∼ 2.5 mm/yr along the stretching direction (N240°E). Superposition of both motions explains the observed left-lateral transtensional regime in the Trans-Alboran shear zone. Two potential driving mechanisms of differential motion of the Alboran-Betic-Gibraltar domain may coexist in the region: a secondary stress source other than plate convergence, related to regional-scale dynamic processes in the upper mantle of the Alboran region, as well as drag from the continental-scale motion of the Nubian plate along the southern limit of the region. In the Atlantic Ocean, the ∼ 3.5 mm/ yr, westward motion of the Gibraltar Arc relative to intraplate Iberia can be accommodated at the transpressive SW-Iberian margin, while available GPS observations do not support an active subduction process in this area.
The 8th June 2008 Mw=6.4 earthquake in NW Peloponnesus: preliminary results from seismic, GPS and field data
On June 8, 2008 at 12:25 UTC a strong earthquake occurred (M=6.4) in NW Peloponnesus, western Gre... more On June 8, 2008 at 12:25 UTC a strong earthquake occurred (M=6.4) in NW Peloponnesus, western Greece. The focal mechanism was determined as strike-slip by several institutions operating in central and eastern Mediterranean. This event is the largest strike-slip earthquake to occur in western Greece during the past 25 years. The hypocentre was located near the village Mihoi in Achaia prefecture (NW Peloponnesus), at a depth of about 18 km. A NOA team conducted field investigation one week after the event. There was no surface rupture. The geology of the area is mostly clastic sedimentary rocks and recent sediments (alluvium). Many rock falls, slides and liquefaction features have been found as is typical for an earthquake of this size. Double-difference relocations of 370 aftershocks show a linear pattern of events and define a clear NE-SW striking main shock fault plane. The aftershock region extends approximately 30 km in length, and the width of the surface projection of the aftershocks is mostly 5 km (max. 10 km). The depth of the aftershocks rarely exceeds 22 km. Analysis of high-rate GPS data from the permanent GPS network of NOA showed that station RLS (Riolos) which is located 12.8 km to the N5°W of the epicentre was displaced co-seismically 7 mm to the North in agreement with right-lateral kinematics of the rupture. Static (Coulomb) stress transfer analysis indicates loading of faults at mid-crustal levels near the towns of Patras (north) and Amaliada (south), respectively. The earthquake put more emphasis on the role of strike-slip faulting in the deformation of western Greece also indicating that seismic strain is partitioned between strike-slip and normal-slip events due to obliquity of the Nubia (Africa) subduction and the N-S extension of the overriding Aegean upper plate.
Active strain-rates across the Messina Straits and kinematics of Sicily and Calabria from GPS data
The Messina Straits is the locus of one of the strongest seismic event that ever hit Italy during... more The Messina Straits is the locus of one of the strongest seismic event that ever hit Italy during historical times, the 1908 Mw 7.1 earthquake, and the same region also suffered major damage from other strong earthquakes in the last few centuries. However, despite the large amount of data and studies carried out, our knowledge of the present-day deformation of this area is still debated. While a general consensus has been reached about the kinematics of the 1908 causative fault, less is known about the rate and shape of interseismic loading across the Straits, and debate continues also about the general kinematics and geodynamic framework of this region which are strongly influenced by subduction and retreat of Ionian lithosphere. Thanks to the increasing number of GPS Networks in the study region it is now possible to study both the regional kinematics and strain loading across active faults. In this work we analyze all the observations collected over the Messina non-permanent GPS Network for the 1994-2008 time span, and data from about 600 CGPS stations in the Euro-Mediterranean region, using the GAMIT software. The output of our analysis is a new and denser velocity field, which is used to study the plate kinematics and the rate of interseismic strain building across the Straits. GPS velocities show a sudden change in their orientation across the Straits moving to NNW-ward, in Estern Sicily, to NNE-ward in Western Calabria, depicting this area as a primary boundary between two different tectonic domains. The maximum strain-rates observed across the Straits are about 120 nanostrain/yr, with extension oriented about normal to the coasts of Sicily according to the presence of a normal fault. The measured velocity gradient can be used to model the creeping dislocation at depth, however, over the Messina Straits the interseismic elastic strains accumulating across other nearby active faults can significantly affect the observed velocity gradient.For this reason we investigate, using a regional elastic block-modeling approach, these effects. We use the block model to test for different microplates configurations and to account for nearby active faults while inverting for optimal fault geometry and intersismic slip-rates across the Straits.
Geophysical Research Letters, 2004
We used earthquake and GPS data to study the present-day kinematics and tectonics of the Africa-E... more We used earthquake and GPS data to study the present-day kinematics and tectonics of the Africa-Eurasia plate boundary in the Western Mediterranean. Crustal seismicity and focal mechanisms outline the geometry of major seismic belts and characterise their tectonics and kinematics. Continuous GPS data have been analyzed to determine Euler vectors for the Nubian and Eurasian plates and to provide the global frame for a new Mediterranean GPS velocity field, obtained by merging continuous and campaign observations. GPS velocities and displacements predicted by the Nubia-Eurasia pole provide estimates of the deformation accommodated across the tectonically active belts. Our analysis reveals a more complex fragmentation of the plate boundary than previously proposed. The roughly E-W trending mainly compressive segments (i.e., southwestern Iberia, northern Algeria and southern Tyrrhenian), where plate convergence is largely accomodated across rather localized deformation zones, and partially transferred northward to the adjacent domains (i.e., the Algero-Balearic and Tyrrhenian basins), are interrupted by regions of more distributed deformation (i.e., the Rif-Alboran-Betics, Tunisia-Libya and eastern Sicily deformation zones), or limited seismicity (i.e., the Strait of Sicily), which are characterized by less homogeneous regimes (mainly transcurrent to extensional). In correspondence of the observed breaks, tectonic structures with different orientation interfere, and we find belts with only limited deformation (i.e., the High and Mid Atlas, the Tunisian Atlas and the offshore Tunisia-Libya belt) that extends from the plate boundary into the Nubian plate, along pre-existing tectonic lineaments. Our analysis suggest that the Sicilian-Pelagian domain is moving independently from Nubia, according to the presence of a right-lateral and extensional decoupling zone corresponding to the Tunisia-Libya and Strait of Sicily deformation zone. Despite the space variability of active tectonic regimes, plate convergence still governs most of the seismotectonic and kinematic setting up to the central Aeolian region. In general, local complexities derive from pre-existing structural features, inherited from the tectonic evolution of the Mediterranean region. On the contrary, along Calabria and the Apennines the contribution of the subducted Ionian oceanic lithosphere and the occurrence of microplates (i.e., Adria) appear to substantially modify both tectonics and kinematics. Finally, GPS data across the Gibraltar Arc and the Tyrrhenian-Calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped.
Geophysical Journal International, 2007
The Western Mediterranean displays a complex pattern of crustal deformation distributed along tec... more The Western Mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence. We used earthquake and Global Positioning System (GPS) data to study the present-day kinematics and tectonics of the Africa-Eurasia plate boundary in this region. Crustal seismicity and focal mechanisms, analysed in terms of seismic moment release and seismic deformation, outline the geometry of major seismic belts and characterize their tectonics and kinematics. Continuous GPS data have been analysed to determine Euler vectors for the Nubian and Eurasian plates and to provide the global frame for a new Mediterranean GPS velocity field, obtained by merging continuous and campaign observations collected in the 1991-2005 time span. GPS velocities and displacements predicted by the Nubia-Eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts. The rather simple deformation occurring in the Atlantic region, characterized by extension about perpendicular to the Middle Atlantic and Terceira ridges and right-lateral motion along the Gloria transform fault, turns into a complex pattern of deformation, occurring along broader seismic belts, where continental lithosphere is involved. Our analysis reveals a more complex fragmentation of the plate boundary than previously proposed. The roughly E-W trending mainly compressive segments (i.e. southwestern Iberia, northern Algeria and southern Tyrrhenian), where plate convergence is largely accomodated across rather localized deformation zones, and partially transferred northward to the adjacent domains (i.e. the Algero-Balearic and Tyrrhenian basins), are interrupted by regions of more distributed deformation (i.e. the Rif-Alboran-Betics, Tunisia-Libya and eastern Sicily) or limited seismicity (i.e. the Strait of Sicily), which are characterized by less homogeneous tectonics regimes (mainly transcurrent to extensional). In correspondence of the observed breaks, tectonic structures with different orientation interfere, and we find belts with only limited deformation (i.e. the High and Middle Atlas, the Tunisian Atlas and the offshore Tunisia-Libya belt) that extends from the plate boundary into the Nubian plate, along pre-existing tectonic lineaments. Our analysis suggest that the Sicilian-Pelagian domain is moving independently from Nubia, according to the presence of a right-lateral and extensional decoupling zone corresponding to the Tunisia-Libya and Strait of Sicily deformation zone. Despite the space variability of active tectonic regimes, plate convergence still governs most of the seismotectonic and kinematic setting up to the central Aeolian region. In general, local complexities derive from pre-existing structural features, inherited from the tectonic evolution of the Mediterranean region. On the contrary, along Calabria and the Apennines the contribution of the subducted Ionian oceanic lithosphere and the occurrence of microplates (i.e. Adria) appear to substantially modify both tectonics and kinematics. Finally, GPS data across the Gibraltar Arc and the Tyrrhenian-Calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped.
Terra Nova, 2007
The tectonics of the central Aeolian Islands, which are located within the Tyrrhenian backarc bas... more The tectonics of the central Aeolian Islands, which are located within the Tyrrhenian backarc basin, has been investigated through a marine seismic reflection survey. We find that compressional structures dominate around the islands, whereas extensional faults occur only to the north of Salina and Filicudi, towards the Marsili basin. This pattern of deformation, although different from previously reported, is in agreement with the strain field and stress regime obtained from GPS measurements and seismological data. Age constraints suggest that contractional deformation was active since middle Pleistocene, being coeval with the building of the volcanic edifices of the Aeolian Islands, and is superimposed on pre-existing extensional deformation. Compressional and extensional regimes, therefore, can coexist within a backarc setting. Seismic profiles show that the Tindari-Letojanni fault, considered as a major tectonic element, does not extend to the north towards the island of Vulcano as a throughgoing fault; rather, deformation is accommodated in a broader belt displaying greater structural complexity.
Geophysical Research Letters, 2004
Geophysical Journal International, 2005
We present a new geodetic velocity solution for Italy and the surrounding areas, obtained from an... more We present a new geodetic velocity solution for Italy and the surrounding areas, obtained from an analysis of continuous and survey-mode Global Positioning System observations collected between 1991 and 2002. We have combined local, regional and global networks into a common reference frame velocity solution, providing a new detailed picture of the regional-scale deformation field in the central Mediterranean. Our velocity estimates are computed with respect to a new stable Eurasian reference frame, constraining the kinematics of the greater African-Eurasian plate boundary system in the study area. We provide strain-rate values for the main seismotectonic districts, which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms. The southern Tyrrhenian area, Calabria, the Apennines, the southeastern Alps, the southern Dinarides and the Albanides display deformation rates at the order of 20-30 nanostrain yr-1. The Corsica-Sardinia block moves according to Eurasian Plate motions, and there is no indication that the opening of the Tyrrhenian is still active. The Pelagian and Sicilian domains are separated by a northwest-southeast discontinuity, the Sicily Channel rifted area, and marginally significant relative motion between the Pelagian Plateau and the African Plate is also observed. The southern Tyrrhenian is affected by north-south compression and accommodates up to 50 per cent of the Africa-Eurasia relative plate motion, whereas the Calabrian Arc exhibits ~2 mm yr-1 northwest-southeast extension. The observed deformation pattern suggests the presence of a major approximately north-south tectonic discontinuity separating the Sicilian and Calabrian domains. An extensional boundary observed along peninsular Italy coincides with the distribution of seismogenic faults along the axis of the Apennines. This boundary separates a Tyrrhenian and an Adriatic domain with diverging velocities, orientated north-NNW-ward and northeastward, respectively. The Apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr-1, and only in the outer northern Apennines indications of active shortening are observed. Insignificant deformation is observed in the western Po Plain and the western Alps, while the central and eastern Alps display north-south shortening. The eastern Adriatic domain is shortening perpendicular to the Dinaric front with strain rates increasing from north to south. The locus of collision between the Aegean/Balkan system and the Adriatic and Ionian domains is marked by the Kephalonia fault system, which accommodates up to 20+/-1 mm yr-1 of right-lateral motion. The deformation pattern observed in the peri-Adriatic domain is well described by a counter-clockwise rotation of the Adriatic microplate around a pole located in the western Alps.
The GIS of the Central Apennines Geodetic Network (CA-GeoNet): Database Description and Application for Crustal Deformation Analysis
During the last few years we set up and surveyed a GPS geodetic network to investigate the active... more During the last few years we set up and surveyed a GPS geodetic network to investigate the active tectonic areas of the Central Apennine, using a combination of permanent and not-permanent geodetic stations. The final goal is to evaluate the geodetic strain rate and the coseismic deformations of this seismically active area. For an optimal management and mapping of the CA-GeoNet (Central Apennine Geodetic Network) a Geographical Information System (GIS) has been developed. The GIS is used to analyze geodetic sources and improve the analysis of crustal deformations and has been realized on PC platform using MapInfo 6.0 and ArcGIS8.1 software. The GIS manages an SQL database consisting of different classes (Geodesy, Topography, Geography, Seismicity and Geology) administrated according to Thematic Layers. A GIS is required for the multidisciplinary approach and management of large multi-scaled data set, geographically referenced and with continuos or discrete coverage; it is particularly designed to analyze GPS sources and to improve crustal deformation analysis related with tectonic structures and seismicity. Through GIS we can display site displacements, strain rate maps and create new layers gained by numerical and spatial analysis. A tailor-made application to support co-seismic deformation scenarios related with historical and instrumental earthquakes and seismic sources, has been created. Our procedures can be successfully applied to design new geodetic networks in seismically active areas with respect to the known seismotectonic features. This dynamic approach in planning and managing GPS networks for geodynamic applications provides a useful tool for geophysical research, earthquake impact and civil protection management.
Geophysical Journal International, 2001
In this paper we present observations of crustal motion related to a large GPS network located in... more In this paper we present observations of crustal motion related to a large GPS network located in the central-western Mediterranean area. Velocities are obtained by the analysis of more than 30 observing sites at which at least three different GPS campaigns were carried out in the time span 1991-1999. The results are presented both in the ITRF96 reference frame and with respect to a Eurasian fixed reference frame. The sites located along the northern African margin, in Sicily and southern Italy show prevalent northeastward movements with a mean velocity of roughly 0.7cmyr-1. The relatively dense network available in the southern Apennines led us to try a tentative estimate of the average strain rate in this zone, resulting in a maximum extension of 0.021+/-0.006×10-6yr-1 normal to the chain. In Ionian Greece the two sites located south of the Kephallinia discontinuity (Lefkas and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15mmyr-1.
The Central Apennine Geodetic Network (CA\GeoNet): Description and Preliminary Results
During the time span 1999-2001 we set up and surveyed the CA-GeoNet (Central Apennine Geodetic Ne... more During the time span 1999-2001 we set up and surveyed the CA-GeoNet (Central Apennine Geodetic Network), a dense sub-regional GPS network located in one of the highest seismic areas of the Apennines (Italy), with the aim to detect the active strain rate of this sector of the chain, during inter-seismic and co-seismic epochs. The network extends across southern Umbria (Norcia area), Abrutii and southern Latium (Sora area) regions and from the Tyrrhenian to the Adriatic sea, in an area of about 130 km x 180 km. It consists of 129 vertices distributed with an average grid of 5 km over the main seismogenetic and geological structures of the area. The non permanent network is linked with the ASI and INGV permanent GPS stations. Among them, INGR, VVLO, ROSE and AQU are deployed E-W in this area, allowing a high precision estimation of the current strain rate component normal to the chain, from Tyrrhenian to Adriatic. Site selection and monumentation were performed after an accurate geological study of the area, with the aim to set up group of stations across the typical basin and ranges seismogenetic structures of the central Apennines, to estimate the strain rate in the near field. To obtain the best accuracy during surveys, the monuments were located on significant outcrops using steel markers screwed in the rock (3D monument) or concrete pillars with deep foundations. Data analysis performed by means of Bernese 4.2 and Gamit software, show accuracy within 1?2 mm in the planar and 1?5 mm in the vertical components, respectively. A preliminary comparison between 1999 and 2001 data for the Rieti and Leonessa sub-network shows horizontal displacements ranging from 5 to 15 mm.
Geophysical Research Letters, 2004
Quaternary International, 2011
This paper provides new relative sea level data inferred from coastal archaeological sites locate... more This paper provides new relative sea level data inferred from coastal archaeological sites located along the Turkish coasts of the Gulf of Fethye (8 sites), and Israel, between Akziv and Caesarea (5 sites). The structures selected are those that, for effective functioning, can be accurately related to sea level at the time of their construction. Thus their positions with respect to present sea level provide a measure of the relative sea level change since their time of construction. Useful information was obtained from the investigated sites spanning an age range ofe2.3ee 1.6 ka BP. The inferred changes in relative sea level for the two areas are distinctly different, from a rise of 2.41 to 4.50 m in Turkey and from 0 to 0.18 m in Israel. Sea level change is the combination of several processes, including vertical tectonics, glacioehydro-isostatic signals associated with the last glacial cycle, and changes in ocean volume. For the Israel section, the present elevations of the MIS-5.5 Tyrrhenian terraces occur at a few meters above present sea level and vertical tectonic displacements are small. Data from GPS and tide gauge measurements also indicate that any recent vertical movements are small. The MIS-5.5 shorelines are absent from the investigated section of the Turkish coast, consistent with crustal subsidence associated with the Hellenic Arc. The isostatic signals for the Israel section of the coast are also small (ranging from À0.11 mm/yr to 0.14 mm/yr, depending on site and earth model) and the observed (eustatic) average sea level change, corrected for this contribution, is a rise of 13.5 AE 2.6 cm during the past e2 ka. This is attributed to the time-integrated contribution to sea level from a combination of thermal expansion and other increases in ocean volume. The observed sea levels from the Turkish sites, in contrast, indicate a much greater rise of up to 2.2 mm/yr since 2.3 ka BP occurring in a wide area between Knidos and Kekova. The isostatic signal here is also one of a rising sea level (of up toe1 mm/yr and site and earthmodel dependent) and the corrected tectonic rate of land subsidence ise1.48 mm/yr. This is the primary cause of dramatic relative sea level rise for this part of the coast.
Geophysical Research Letters, 2009
Crustal deformations in Italy and surrounding regions inferred from GPS data and earthquakes focal mechanisms
The joint analysis of geodetic, seismological and geological information on the spatial distribut... more The joint analysis of geodetic, seismological and geological information on the spatial distribution of crustal deformations is revealing new insights in the understanding of the kinematics and dynamics of the complex plate boundary system present in the central Mediterranean. In this work we compare results obtained from the analysis of more than 10 years of GPS data, collected on more than 130 geodetic sites distributed in the European and Mediterranean areas, with the information provided by 25 years of focal mechanisms for earthquakes with M>4.5, as provided by Harvard CMT catalogue and INGV Euro-Mediterranean Regional Centroid Moment Tensor (RCMT) data base. GPS data have been collected at different scales, and have been used to constraint the kinematics of both major tectonic plates and crustal blocks in the study area. The central Mediterranean area is presently characterized by a relatively high number of crustal blocks, as consequence of the space and time evolution of the African/Eurasian plate boundary system. Considering the structural complexity and the relatively low deformation rates of the study area, we improved resolution of the available geodetic information rigorously combining GPS observations performed at permanent stations managed by different Italian and European institutions, for the time span 1998-2002, with survey mode GPS data, collected on several geodetic networks in the time span 1991-2002, by the University of Bologna and INGV. Following a distributed session approach, regional and local solutions have been combined with EUREF and IGS global solutions. The whole data set has been analyzed using a uniform processing strategy, significantly reducing reference frame biases. Horizontal velocities of a set of IGS stations have been used to evaluate a stable European frame, and the relative kinematics of African and Eurasian plates has been tentatively constrained. An analysis in terms of rigid-block motions has been performed and a kinematics interpretation has been carried out, delineating some first-order crustal wedges, and tentatively constraining the kinematics of major tectonics boundaries that interest this region. The long-wavelength geodetic strain rate field has been computed and compared with the strain field obtained from the analysis of earthquake focal mechanisms. Significant coherence, in terms of style of deformation, between geodetic and seismic strain fields has been obtained in most of the study area.
Geophysical Journal International, 2001
In this paper we present observations of crustal motion related to a large GPS network located in... more In this paper we present observations of crustal motion related to a large GPS network located in the central-western Mediterranean area. Velocities are obtained by the analysis of more than 30 observing sites at which at least three different GPS campaigns were carried out in the time span 1991–1999. The results are presented both in the ITRF96 reference frame and with respect to a Eurasian fixed reference frame. The sites located along the northern African margin, in Sicily and southern Italy show prevalent northeastward movements with a mean velocity of roughly 0.7 cm yr−1. The relatively dense network available in the southern Apennines led us to try a tentative estimate of the average strain rate in this zone, resulting in a maximum extension of 0.021 ± 0.006 × 10−6 yr−1 normal to the chain. In Ionian Greece the two sites located south of the Kephallinia discontinuity (Lefkas and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr−1.
We use GPS velocities and dislocation modeling to investigate the rate and shape of interseismic ... more We use GPS velocities and dislocation modeling to investigate the rate and shape of interseismic strain loading in the area affected by the 1908 Mw 7.1 Messina earthquake (southern Italy) in the framework of the complex central Mediterranean micro-plates kinematics. Our data confirm the change in the velocity trends between Sicily and Calabria, moving from NNW-ward to NE-ward, and details a fan-like pattern across the Straits where maximum extensional strain-rates are ~90 nanostrain/yr, oriented normal to the coasts of Sicily, according to the presence of SW-NE trending normal faults driving contemporary crustal deformation. Half space dislocation modeling of GPS velocities is used to infer the interseismic slip-rates and geometric fault parameters, obtaining optimal values of 3.4 and 1.8 mm/yr for the dip-slip and strike-slip components, respectively, along a 30° dipping normal fault, locked at 7.8 Km depth. By developing a regional elastic block model that account for both crustal blocks rotations and strain loading at block-bounding faults, we show that the measured velocity gradient across the Straits may be significantly affected by the elastic strain contribute of other nearby active faults. In particular, seeking for signals of the possibly locked Calabrian subduction interface onto the observed velocity gradients in NE-Sicily and SW-Calabria, we find that this longer wavelength signal can be presently super-imposed on the observed velocity gradients in NE-Sicily and Calabria, whereas, minor effects are expected for other nearby faults. Our analysis, if from one side measures the current state of strain building in a highly seismically hazardous area, also put new lights on the potential seismic hazard of the wider Sicily and Calabria region.
GPS measurements of crustal deformation across the northern Apennines, Italy
Late Cenozoic deformation of the northern Apennines (Italy) has attracted scientific interest for... more Late Cenozoic deformation of the northern Apennines (Italy) has attracted scientific interest for decades, but community consensus regarding active deformation of the orogen, particularly regarding activity within the foreland thrust belt, has not yet emerged. We present crustal deformation results from a geodetic experiment focused on the northern Apennines orogen. The experiment centers on 32 benchmarks measured with GPS annually between 2003 and 2007, supplemented by data from an additional older set of 6 campaign stations, and 210 continuous GPS stations within and around northern Italy. RMS variations of daily position estimates about a simple constant velocity kinematic model range between 1-2/4-9 mm (horizontal/vertical) for continuous stations, 2-5/5-14 mm for new campaigns, and 2-6/5-36 mm for older campaigns. Velocity uncertainties are well below the 1 mm/yr level for continuous stations, and at or below 1 mm/yr for most campaign stations. The new data set reveals the present-day pattern of deformation across the northern Apennines with significantly higher spatial resolution than previous studies, and allows for a new assessment of modern deformation within the orogen and across the foreland thrust belt. Maximum rates within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen. A smaller fraction of this motion is also accommodated by shortening across the thrust belt to the northeast of the range, but the strain rate field across the thrust region is complex, involving shear and/or local rotation in addition to shortening.
Earth and Planetary Science Letters, 2010
We use Global Positioning System (GPS) velocities and dislocation modeling to investigate the rat... more We use Global Positioning System (GPS) velocities and dislocation modeling to investigate the rate and nature of interseismic strain accumulation in the area affected by the 1908 Mw 7.1 Messina earthquake (southern Italy) within the framework of the complex central Mediterranean microplate kinematics. Our data confirm a change in the velocity trends between Sicily and Calabria, moving from NNW-ward to NEward with respect to Eurasia, and detail a fan-like pattern across the Messina Straits where maximum extensional strain rates are~65 nanostrains/yr. Extension normal to the coast of northern Sicily is consistent with the presence of SW-NE trending normal faults. Half-space dislocation models of the GPS velocities are used to infer the slip-rates and geometric fault parameters of the fault zone that ruptured in the Messina earthquake. The inversion, and the bootstrap analysis of model uncertainties, finds optimal values of 3. 5 + 2.0 − 1.3 and 1.6 + 0.3 − 0.2 mm/yr for the dip-slip and strike-slip components, respectively, along a 30 + 1.1 − 0.7°S E-ward dipping normal fault, locked above 7.6 + 4.6 − 2.9 km depth. By developing a regional elastic block model that accounts for both crustal block rotations and strain loading at block-bounding faults, and adopting two different competing models for the Ionian-Calabria convergence rates, we show that the measured velocity gradient across the Messina Straits may be significantly affected by the elastic strain contribution from other nearby faults. In particular, when considering the contribution of the possibly locked Calabrian subduction interface onto the observed velocity gradients in NE-Sicily and western Calabria, we find that this longer wavelength signal can be presently super-imposed on the observed velocity gradients in NE-Sicily and Calabria. The inferred slip-rate on the Messina Fault is significantly impacted by elastic strain from the subduction thrust. By varying the locking of the subduction thrust fault, in fact, the Messina Fault slip-rate varies from 0 to 9 mm/yr.
Uploads
Papers by Enrico Serpelloni