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Collettini, Cristiano
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Collettini, Cristiano
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cristiano.collettini@uniroma1.it
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- PublicationOpen AccessFrom mapped faults to fault-length earthquake magnitude (FLEM): a test on Italy with methodological implications(2019)
; ; ; ; ; ; ; ; ; ; ; ; ;; ;; ; ; ;Empirical scaling relationships between fault or slip dimensions and earthquake magnitudes are often used to assess the maximum possible earthquake magnitude of a territory. Upon the assumption of the reactivability of any fault, the earthquake magnitudes derived from the surface fault length (FLEM) are compared at the national scale in Italy against catalogued magnitudes. FLEMs are obtained by considering a comprehensive fault dataset regardless of fault age, stress field orientation, strain rate, etc. In particular, (1) a comprehensive catalogue of all known faults is compiled by merging the most complete databases available; (2) FLEM is then derived from fault length; and (3) the resulting FLEMs are compared (i.e. the mathematical difference) with catalogued earthquake magnitudes. Results show that the largest FLEMs as well as the largest differences between FLEMs and catalogued magnitudes are observed for poorly constrained faults, mainly inferred from subsurface data. It is suggested that these areas have to be further characterized to better estimate fault dimension and segmentation and hence properly assess the FLEM. Where, in contrast, the knowledge of faults is geologically well constrained, the calculated FLEM is often consistent with the catalogued seismicity, with the 2 value of the distribution of differences being 1.47 and reducing to 0.53 when considering only the Mw 6:5 earthquakes. Our work highlights areas, in Italy, where further detailed studies on faults are required.225 54 - PublicationRestrictedArchitecture and mechanics of an active low-angle normal fault: Alto Tiberina Fault, northern Apennines, Italy(2007-10-25)
; ; ; ; ; ;Chiaraluce, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Chiarabba, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Collettini, C.; Univ. di Perugia ;Piccinini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; We present seismological evidence for the existence of an actively slipping low angle normal fault (15¡ã dip) located in the Northern Apennines of Italy. During a temporary seismic experiment, we recorded ~2000 earthquakes with ML ¡Ý 3.1. The micro-seismicity defines a 500 to 1000 m thick fault zone that cross-cuts the upper crust from 4 km down to 16 km depth. The fault coincides with the geometry and location of the Alto Tiberina Fault (ATF) as derived from geological observations and interpretation of depth-converted seismic reflection profiles. In the ATF hangingwall the seismicity distributions highlight minor synthetic and antithetic normal faults (4-5 km long) that sole into the detachment. The ATF related seismicity shows a nearly constant rate of earthquake production, ~ 3 events per day (ML ¡Ü 2.3), and a higher b-value (1.06) with respect to the fault hanging-wall (0.85) which is characterized by a higher rate of seismicity. In the ATF-zone we also observe the presence of clusters of earthquakes occurring with relatively short time delays and rupturing the same fault patch. To explain movements on the ATF, oriented at high angles (~75¡ã) to the maximum vertical principal stress, we suggest an interpretative model in which crustal extension along the fault is mostly accommodated by aseismic slip in velocity strengthening areas whilst micro-earthquakes occur in velocity weakening patches. We propose that these short-lived frictional instabilities are triggered by fluid overpressures related to the build-up of CO2¨Crich fluids as documented by boreholes in the footwall of the ATF.223 46 - PublicationEmbargoY-B-P-R or S-C-C′? Suggestion for the nomenclature of experimental brittle fault fabric in phyllosilicate-granular mixturesMineralogy, fabric, and frictional properties are fundamental aspects of faults. Despite the extensive effort spent in the characterization of such fault properties, the description of fabric elements is not always univocal and nomenclatures such as the Y-B-P-R and the S-C-C′ are at times used interchangeably. This work presents a sys- tematic mineralogical, microstructural, and frictional characterization of natural gouges designed to constrain a criterion for the distinction between the Y-B-P-R and S-C-C′ fabric. For this purpose, we tested four representative natural mixtures of granular minerals (quartz) with increasing amount of phyllosilicates (muscovite). 24 fric- tional experiments were performed at constant normal stresses of 25, 50, 75 and 100 MPa, at both room dry and water saturated condition. We document that Y-B-P-R fabric typically develops in frictionally strong, granular- rich experimental faults. This fabric is associated to strain localization in narrow shear zones characterized by intense grain size reduction and dominant cataclastic processes. Conversely, S-C-C′ fabric is observed in phyllosilicate-rich experimental faults, which are characterized by distributed deformation and pervasive foli- ation. Deformation is mainly accommodated by frictional sliding along the well-oriented phyllosilicate foliae. The transition from Y-B-P-R to S-C-C′ is observed for phyllosilicates content >30% and is facilitated by secondary mechanical processes as networking of phyllosilicates and grain mantling. The evolution from Y-B-P-R to S-C-C′ fabric is also associated with a marked reduction in friction, in healing rate and changes in the rate and state friction parameters. Despite their geometrical similarities, we show that Y-B-P-R and S-C-C′ represent distinct fabrics reflecting the dichotomy that exists between frictionally strong, granular-rich, and frictionally weak, phyllosilicate-rich faults.
29 6 - PublicationRestrictedThe role of rheology, crustal structures and lithology in the seismicity distribution of the northern Apennines(2017-01-02)
; ; ; ; ; ; ; ; ;; ; ; ;The Northern Apennines of Italy is a unique area to study active crustal processes due to the availability of high-resolution subsurface geology (deep borehole and seismic profiles) and seismicity (back-ground and seismic sequences) data. In this work we have investigated the relationship between crustal structures and lithologies, rheological profiles and seismicity cut-off by constructing three integrated profiles across the Umbria-Marche Apennines. At first approximation we observe a good correspondence between the background seismicity cut-off and the modelled brittle ductile transition (BDT): 90% of the seismic activity is located above the transition. In the area characterized by active extension, where the majority of the seismicity is occurring, most of the crustal earthquakes are confined within the brittle layer at depth < 12 km. In areas where the brittle layer is affected by regional structures, we observe an active role played by these structures in driving the seismicity distribution. One example is the region where the gently eastward dipping Altotiberina low-angle normal fault is present, where the seismicity cut-off is completely controlled by this detachment that separates an active hanging-wall from an almost aseismic foot-wall block. At smaller scale also the lithology plays a strong control on the seismicity distribution. We observe that the largest earthquakes of the area, 5.5 < M < 6.0, do not nucleate at the base of the BDT but they occur at the base of the sedimentary cover. Our work suggests that rheology and therefore the position of the brittle ductile transition exerts a role at regional scale for the occurrence of crustal seismicity, however crustal structures and lithology play the major role at a more local scale and therefore they need to be considered for a better understanding of earthquake distribution within the seismogenic layer.554 109 - PublicationRestrictedEvolution of shear fabric in granular fault gouge from stable sliding to stick slip and implications for fault slip mode(2017-08)
; ; ; ; ; ; ; ; ; Laboratory and theoretical studies provide insight into the mechanisms that control earthquake nucleation, when fault slip velocity is slow (<0.001 cm/s), and dynamic rupture when fault slip rates exceed centimeters per second. The application of these results to tectonic faults requires information about fabric evolution with shear and its impact on the mode of faulting. Here we report on laboratory experiments that illuminate the evolution of shear fabric and its role in controlling the transition from stable sliding (v ∼0.001 cm/s) to dynamic stick slip (v > 1 cm/s). The full range of fault slip modes was achieved by controlling the ratio K = k/kc, where k is the elastic loading stiffness and kc is the fault zone critical rheologic stiffness. We show that K controls the transition from slow-and-silent slip (K > 0.9) to fast-and-audible (K < 0.7, v = 3 cm/s, slip duration 0.003 s) slip events. Microstructural observations show that with accumulated strain, deformation concentrates in shear zones containing sharp shear planes made of nanoscale grains, which favor the development of frictional instabilities. Once this fabric is established, fault fabric does not change significantly with slip velocity, and fault slip behavior is mainly controlled by the interplay between the rheological properties of the slipping planes and fault zone stiffness.116 5 - PublicationOpen AccessThe architecture and mechanics of an active low angle normal fault: the Alto Tiberina Fault, northern Apennines, Italy(2007-09-25)
; ; ; ; ; ;Chiaraluce, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Chiarabba, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Collettini, C.; Univ. Perugia, Italy ;Piccinini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cocco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ;Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Bernabé, Y.see Abstract Volume164 538 - PublicationOpen AccessUSEMS & GLASS: investigator-driven frontier research in earthquake physics. Ground-breaking research in Europe enhances outreach to the general public.(2011-12-05)
; ; ; ;Mariano, Sofia; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Di Toro, Giulio; Padua University ;Collettini, Cristiano; Perugia University; ; ; Session, EducationUSEMS and GLASS are two projects financed by the European Research Council (ERC) as part of the ERC starting grants scheme within the FP7 framework. The rationale behind the funding scheme is to support some of the most promising scientific endeavours in Europe that are being led by young researchers, and to emphasize the excellence of individual ideas rather than specific research areas; in other words, to promote bottom-up frontier research. The general benefits of this rationale are evident in the two ongoing projects that deal with earthquake physics, as these projects are increasingly recognized in their scientific community. We can say that putting excellence at the heart of European Research strongly contributes to the construction of a European knowledge-based society. From a researcher point-of-view one of the most challenging aspects of these projects is to approach and convey the results of the projects to a general public, contributing actually to the construction of knowledge-based society. Luckily, media interest and the availability of a number of new communication tools facilitate the outreach of scientific achievements. The largest earthquakes during the last ten years (e.g. Sumatra 2004 and Japan 2011) have received widespread attention in the media world (TV, W.W.W., Newspaper and so on) for months, and successful research projects such as those above also become media protagonists, gaining their space in the media bullring. The USEMS principal investigator and his team have participated in several dissemination events in the Mass Media, such as interviews wit Italian and French TV national broadcasts (RAI Due TG2, RAI Uno Unomattina, Rai Tre Geo & Geo, FRANCE 2); interviews in scientific journals: SCIENCE (Sept. 2010), newspapers and web (Corriere della Sera, Il Gazzettino, Il Messagero, La Stampa, Libero, Il Mattino, Yahoo, ANSA, AdnKronos and AGI); radio (RadioRai Uno, RadioRai Tre Scienza); documentary “Die Eroberung der Alpen” produced by Tangram Film (Munchen, Germany). The USEMS project started in June 2008, and the GLASS project in October 2010. For both projects we developed a number of web pages through the official web site of the host institution, the National Institute of Geophysics and Volcanology (INGV) in Rome. In these pages we describe the projects, publish pictures and short-movies of the experimental activities and keep the project results up to date. In addition the research teams collaborate within various INGV outreach schemes (school and student visits in the laboratory, writing short news reports for the INGV press office, and interviews with journalists) as well as using WWW channels (Facebook, Youtube) to make the project results available to the general public. Finally, it is notable that the ERC funding agency itself is fully involved in the outreach activities using its own communication channels and its highly skilled resources which promote through brochures, web pages, publications and documentaries the best projects. We are going to improve our effort in this direction up to the end of the projects.182 143 - PublicationOpen AccessA new biaxial apparatus integrated within a pressure vessel to test the physical properties of brittle rock: the state-of-the-art(2012-08-16)
; ; ; ; ; ; ; ; ;Di Stefano, Giuseppe; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Collettini, Cristiano; Universita' Perugia, Italy ;Carpenter, Brett; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Mollo, Silvio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Romeo, Giovanni; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Scarlato, Piergiorgio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tesei, Telemaco; Universita' Perugia, Italy ;Vinciguerra, Sergio; Universita' Torino, Italy; ; ; ; ; ; ; A main goal of the European Research Council, Starting Grant, GLASS (InteGrated Laboratories to investigate the mechanics of ASeismic vs Seismic faulting), is to develop a prototype rock deformation biaxial apparatus to examine the physical properties of brittle rocks. Two layers of fault rock are sandwiched between three steel block by a normal load applied using a horizontal oil-dynamics piston. A vertical oil-dynamics piston pushes the internal rock sample of the sandwich in order to slide at constant velocity. With GLASS we are going to build-up a confining pressure around the rock samples under load stress (tri-axial mode) and to measure the fluid flow properties of the rock during the deformation. Working in tri-axial mode with a fluid circulation, the machine is able to measure and to characterize frictional properties of faults on the sample for a wide spectrum of realistic conditions. We have concurrently been working to improve the control and the acquisition system for having a machine very flexible and easy to use for several applications and capable to detect different signals on the rock during frictional sliding in a fluid-rich environment with the goal of comparing these signals to those observed in nature. We began designing the servo controlled machine in October 2010 and have recently installed the apparatus in the HP-HT lab at the INGV in Rome. First tests of this biaxial apparatus confirm the main target of the project.275 181 - PublicationOpen AccessBifurcations at the Stability Transition of Earthquake Faulting(2020)
; ; ; ; ; ; ; ; ; ; ; Tectonic faults typically break in a single rupture mode within the range of styles from slow slip to dynamic earthquake failure. However, in increasingly well‐documented instances, the same fault segment fails in both slow and fast modes within a short period, as in the sequences that culminated in the 2011 Mw = 9.0 Tohoku‐Oki, Japan, and 2014 Mw = 8.2 Iquique, Chile, earthquakes. Why slow slip alternates with dynamic rupture in certain regions but not in others is not well understood. Here, we integrate laboratory experiments and numerical simulations to investigate the physical conditions leading to cycles where the two rupture styles alternate. We show that a bifurcation takes place near the stability transition with sequences encompassing various rupture modes under constant loading rate. The range of frictional instabilities and slip cycles identified in this study represents important end‐members to understand the interaction of slow and fast slip on the same fault segment.64 10 - PublicationOpen AccessFrictional Strengthening Explored During Non‐Steady State Shearing: Implications for Fault Stability and Slip Event Recurrence Time(2020)
; ; ; ; ; ; ; ; ; On natural faults that host repeating slip events, the inter‐event loading time is quite large compared to the slip event duration. Since most friction studies focus on steady‐state frictional behavior, the fault loading phase is not typically examined. Here, we employ a method specifically designed to evaluate fault strength evolution during active loading, under shear driving rates as low as 10−10 m/s, on natural fault gouge samples from the Waikukupa Thrust in southern New Zealand. These tests reveal that in the early stages of loading following a slip event, there is a period of increased stability, which fades with accumulated slip. In the framework of rate‐ and state‐dependent friction laws, this temporary stable phase exists as long as slip is less than the critical slip distance and the elapsed time is less than the value of the state variable at steady state. These observations indicate a minimum earthquake recurrence time, which depends on the field value of the critical slip distance and the background slip rate. We compare estimates of minimum earthquake recurrence times with the recurrence times of repeating large earthquakes on the Alpine Fault in southern New Zealand and repeating small‐magnitude earthquakes on the San Andreas Fault system in California. We find that the observed recurrence times are mostly longer than the predicted minimum values, and exceptions in the San Andreas system may be explained by elevated slip rates due to larger earthquakes in this region.62 14