On the use of simulated annealing method and cross-validation theory for deconvolution of seismograms Bull

Abstract In order to retrieve the apparent source time function (ASTF) seen at a given station, one must take into account propagation effects, site, and instrumental influences. Removing these effects can be performed by a deconvolution of the mainshock seismogram by a seismogram of a smaller event recorded at the same station. This smaller event must occur nearby the mainshock, and the associated seismogram is considered as an empirical Green's function. We propose a deconvolution based on the simulated annealing method, and we compare it with the often-used spectral division technique. We show on both synthetic and real signals that the simulated annealing deconvolution (SAD) provides stable and positive ASTF, whereas results from spectral division are very sensitive to an ad hoc parameter called water level. Finally, the application of cross-validation analysis between the three components of the seismogram in addition to the SAD allows us to estimate errors on the ASTF

Rupture history of the 1997 Umbria-Marche (Central Italy) main shocks from the inversion of GPS, DInSAR and near field strong motion data

We investigate the rupture history of the three largest magnitude earthquakes of the 1997 Umbria-Marche sequence by inverting GPS, DInSAR and near-source strong motion waveforms. We use the frequency domain inversion procedure proposed by Cotton and Campillo (1995) and calculate the Green s functions for a layered halfspace using the discrete wavenumber and reflectivity methods. We first invert GPS measurements and DInSAR interferograms to image the coseismic slip distribution on the fault planes in a layered half space for the two earthquakes that occurred on September 26, 1997 at 00:33 UTC (Mw = 5.7) and 09:40 UTC (Mw = 6.0) near Colfiorito. We also invert DInSAR interferograms to infer the slip distribution during the subsequent earthquake that occurred on October 14, 1997 at 15:23 UTC (Mw = 5.6) in the SE section of the seismogenic zone near Sellano. We also explore the set of acceptable solutions using a genetic algorithm to have information on the available resolution of geodetic data. The slip models obtained by geodetic data inversion are used to perform a forward modeling of strong motion waveforms for all three events. We adopt a constant rupture velocity of 2.6 km/s and a constant rise time of 1 s. Our results show that these rupture models provide an acceptable fit to recorded waveforms. Finally, we invert the recorded ground displacements, collected during the September 26th 09:40 main shock and the October 14th Sellano earthquake, to constrain the rupture history. We use the geodetic slip distribution as starting model for the iterative inversion procedure. The retrieved rupture models are consistent with those inferred from geodetic data and yield a good fit to recorded seismograms. These rupture models are characterized by a heterogeneous slip distribution and an evident rupture directivity in agreement with previous observations

The "O3E" program: raising awareness on natural hazards

Earthquakes may be traumatic events and as many other environmental emergencies, like storm or floods, may cause more damages than expected when who experiences the phenomena does not know how to behave in the fall. Provided that it is always not feasible to rely on prediction when dealing with earthquakes or extreme meteorological events, preparedness proves to be an efficient (and certainly the most recommendable and cheap) way to face emergencies. Education and training are thus two ingredients to help citizens to perceive the scientific information formerly confined in the laboratories, in particular in the domain of the environmental risk. The “O3E” innovative program (European Observatory for Education and Environment) is established after 10 years (1997-2007) of regional and national original programs (“Sismos of the Schools”), and from Italian and Swiss experiences concerning environment tools for education. The project, that is a cooperation between France, Italy and Switzerland, is born to promote a responsible behaviour of citizens in front of the evolution of a society where scientific information is promptly available. ARGAL (Agency for Geological Risk in the Latin Arc) operates the administrative and technical coordination. The objective of this program is to create a school network in the Alpine and Mediterranean areas equipped with environmental sensors of an educational vocation. The data on the movement of the ground (seismometers), the temperatures and precipitations (weather stations), the flows of rivers (hydrogeology) recorded in the schools and processed by the students are collected on dedicated servers and then made available through internet to the entire educational community. This network “O3E”, once installed, is the starting point of activities. Indeed, various general objectives are pursued: - To promote the applied sciences and new technologies. - To put in network the actors of Education and formation. - To develop the sense of the autonomy and the responsibility in the young people. - To reinforce and develop relationships with regional partners of the educational and university fields. - To support a rational awakening for the prevention of the natural risks that can make the difference during the event in terms of safety. With these premises, the “O3E” experience sets up a permanent educational network of citizens in the Alpine and Mediterranean areas, building an exchange of knowledge on natural risks prevention.PublishedAix en Provence5.9. Formazione e informazioneope

The Grosmarin experiment

The GROSMARIN (which stands for GrandROSMARIN) cruise is proposed by UMR Géosciences Azur (with fellow french and italian research groups). Its goals are to better characterize active structures along this zone and to assess the resulting seismic hazard in a sort of continuation with respect to the MALISAR experiment, which has already surveyed some active structures through shallow observations. The GROSMARIN cruise is in fact the necessary counterpart to characterize them at depth

Il progetto “O3E” I rischi naturali divulgati nella scuola per produrre conoscenza e consapevolezza

“O3E” (Observation de l’Environnement à but educatif dans les Écoles” ovvero osservazione dell'Ambiente a scopo educativo nella scuola) è un progetto transfrontaliero di educazione all’ambiente che raggruppa tre discipline (sismologia, meteorologia ed idrologia) ed è destinato agli allievi che frequentano le scuole primarie, medie ma soprattutto superiori nell’area delle Alpi latine. L'utilizzo di stazioni di misura nell'ambito delle scuole, delle attività pedagogiche “chiavi in mano”, il contatto tra scienziati ed insegnanti, un sito web che permette di visualizzare i dati “on line” ed il trasferimento transfrontaliero di conoscenze che riguardano l’educazione all’ambiente rappresentano le principali originalità del progetto “O3E”.Published48-491TM. Formazione2TM. Divulgazione ScientificaN/A or not JCRope

The "O3E" program: raising awareness on natural hazards

Earthquakes may be traumatic events and as many other environmental emergencies, like storm or floods, may cause more damages than expected when who experiences the phenomena does not know how to behave in the fall. Provided that it is always not feasible to rely on prediction when dealing with earthquakes or extreme meteorological events, preparedness proves to be an efficient (and certainly the most recommendable and cheap) way to face emergencies. Education and training are thus two ingredients to help citizens to perceive the scientific information formerly confined in the laboratories, in particular in the domain of the environmental risk. The “O3E” innovative program (European Observatory for Education and Environment) is established after 10 years (1997-2007) of regional and national original programs (“Sismos of the Schools”), and from Italian and Swiss experiences concerning environment tools for education. The project, that is a cooperation between France, Italy and Switzerland, is born to promote a responsible behaviour of citizens in front of the evolution of a society where scientific information is promptly available. ARGAL (Agency for Geological Risk in the Latin Arc) operates the administrative and technical coordination. The objective of this program is to create a school network in the Alpine and Mediterranean areas equipped with environmental sensors of an educational vocation. The data on the movement of the ground (seismometers), the temperatures and precipitations (weather stations), the flows of rivers (hydrogeology) recorded in the schools and processed by the students are collected on dedicated servers and then made available through internet to the entire educational community. This network “O3E”, once installed, is the starting point of activities. Indeed, various general objectives are pursued: - To promote the applied sciences and new technologies. - To put in network the actors of Education and formation. - To develop the sense of the autonomy and the responsibility in the young people. - To reinforce and develop relationships with regional partners of the educational and university fields. - To support a rational awakening for the prevention of the natural risks that can make the difference during the event in terms of safety. With these premises, the “O3E” experience sets up a permanent educational network of citizens in the Alpine and Mediterranean areas, building an exchange of knowledge on natural risks prevention

Citizen seismology helps decipher the 2021 Haiti earthquake

5 pages, 4 figures, supplementary materials https://doi.org/10.1126/science.abn1045.-- Data and materials availability: All data and code used in this study are openly available. RADAR data can be obtained through ESA (Sentinel) or JAXA (Alos-2). Aftershock data can be obtained from https://ayiti.unice.fr/ayiti-seismes/ (7). The codes used to process or model the data are published and public (8). The catalog of high-precision earthquake relocated with the NLL-SSST-coherence procedure (SM4) is available as supplementary dataOn 14 August 2021, the moment magnitude (Mw) 7.2 Nippes earthquake in Haiti occurred within the same fault zone as its devastating 2010 Mw 7.0 predecessor, but struck the country when field access was limited by insecurity and conventional seismometers from the national network were inoperative. A network of citizen seismometers installed in 2019 provided near-field data critical to rapidly understand the mechanism of the mainshock and monitor its aftershock sequence. Their real-time data defined two aftershock clusters that coincide with two areas of coseismic slip derived from inversions of conventional seismological and geodetic data. Machine learning applied to data from the citizen seismometer closest to the mainshock allows us to forecast aftershocks as accurately as with the network-derived catalog. This shows the utility of citizen science contributing to our understanding of a major earthquakeThis work was supported by the Centre National de la Recherche Scientifique (CNRS) and the Institut de Recherche pour le Développement (IRD) through their “Natural Hazard” program (E.C., S.S., T.M., B.D., F.C., J.P.A., J.C., A.D., D.B., S.P.); the FEDER European Community program within the Interreg Caraïbes “PREST” project (E.C., S.S., D.B.); Institut Universitaire de France (E.C., R.J.); Université Côte d’Azur and the French Embassy in Haiti (S.P.); the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant no. 758210, Geo4D project to R.J. and grant no. 805256 to Z.D.); the French National Research Agency (project ANR-21-CE03-0010 “OSMOSE” to E.C. and ANR-15-IDEX-01 “UCAJEDI Investments in the Future” to Q.B.); the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant no. 949221 to Q.B.); and HPC resources of IDRIS (under allocations 2020-AD011012142, 2021-AP011012536, and 2021-A0101012314 to Q.B.With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

The Mw = 6.3, November 21, 2004, Les Saintes earthquake (Guadeloupe): Tectonic setting, slip model and static stress changes,

International audienceOn November 21, 2004, a magnitude 6.3 earthquake occurred offshore, 10 km south of Les Saintes archipelago in Guadeloupe (French West Indies). There were more than 30000 aftershocks recorded in the following two years, most of them at shallow depth near the islands of the archipelago. The main shock and its main aftershock of February 14, 2005 (Mw = 5.8) ruptured a NE-dipping normal fault (Roseau fault), mapped and identified as active from high-resolution bathymetric data a few years before. This fault belongs to an arc-parallel en echelon fault system that follows the inner edge of the northern part of the Lesser Antilles arc, accommodating the sinistral component of oblique convergence between the North American and Caribbean plates. The distribution of aftershocks and damage (destruction and landslides) are consistent with the main fault plane location and attitude. The slip model of the main shock, obtained by inverting jointly global broadband and local strong motion records, is characterized by two main slip zones located 5 to 10 km to the SE and NW of the hypocenter. The main shock is shown to have increased the Coulomb stress at the tips of the ruptured plane by more than 4 bars where most of the aftershocks occurred, implying that failures on fault system were mainly promoted by static stress changes. The earthquake also had an effect on volcanic activity since the Boiling Lake in Dominica drained twice, probably as a result of the extensional strain induced by the earthquake and its main aftershock

Verso una migliore conoscenza delle strutture del margine Ligure: il progetto GROSMARIN

(English Abstract) The Ligurian margin, that is the junction area located between the Ligurian basin and the Southwestern Alps, is a passive margin, seismically active and subjected to gravitative movements. The active deformation in this sector is among the strongest ever experienced in Western Italy and Southern France. The current geodynamics of the basin is not completely understood yet, and somewhat under interest and debate of the scientific community. The latest results on the recent evolution of the Alps-Mediterranean system suggest that the area under study lay close to a domain under extension. The interest for the area is reinforced by its seismic activity that, although of low to moderate energy, acts in an area of high vulnerability. Some historical events involved in fact dramatic social and material damages. The growth of population (that now accounts for more than 2.500.000 inhabitants between Cannes and Genoa), the setting of numerous industries and the tourist business of the area are additional motivation for monitoring the area from the seismic point of view and especially to make specific studies on the seismogenic structures of this sector. Events with magnitude greater than 4.5 to 5.0 are in fact recorded every 5 years, but the area undergoes a rather weak microseismicity that often remains undetected and always poorly located by land seismic networks. The natural risks associated to this sector cannot neglect the presence of steep canyons that incise the offshore margin and favour gravitative slopes. The sediment masses accumulate on top of these canyons and may slip even after an earthquake of moderate magnitude. The GROSMARIN (which stands for GrandROSMARIN) cruise is proposed by UMR Géosciences Azur (with fellow french and italian research groups). It aims at (1) studying the microseismicity along a part of the northern margin of the Ligurian Basin, offshore France and Italy and (2) to realise a 3D tomography by wide-angle seismics. The goal is to better characterize active structures along this zone and to assess the resulting seismic hazard.Published359-360N/A or not JCRope