Spatiotemporal evolution of surface creep in the Parkfield region of the San Andreas Fault (1993-2004) from synthetic aperture radar.

International audienceThe Parkfield section of the San Andreas Fault (SAF) is defined as a transitional portion of the fault between slip-release behavior types in the creeping section of the SAF to the northwest and the apparently locked section to the southeast. The Parkfield section is characterized by complex frictional fault behavior because it represents a transition zone from aseismic creep to stick-slip regime. At least six historic earthquakes of Mw ~6 have occurred in this area in 1881, 1901, 1922, 1934, 1966, and 2004. It was observed in the 2004 Mw 6.0 Parkfield earthquake that ~70% of the total (coseismic and postseismic) moment release occurred aseismically. To understand the SAF behavior in this area, it is of particular interest to measure and analyze, not only the spatial evolution of the surface displacement in this area, but also its evolution over time. Using radar data acquired by the European Space Agency's European Remote Sensing (ERS1-2) satellites, we constructed descending interferograms and retrieved time series of surface displacements along the central SAF for the decade preceding the 2004 Parkfield earthquake. We focus on characterizing the space and time evolution of surface creep in the Parkfield and Cholame sections. The spatial pattern of the interseismic displacement rate indicates that tectonic strain was not uniformly distributed along the strike of the fault between 1993 and 2004. Our data indicate not only a decrease in the creep rate from the Parkfield section to south of Highway-46 from 1.4 ±0.3 cm/y to 0.6 ±0.3 cm/y, but also a small but significant creep-rate increase in the Cholame section to 0.2 ±0.1 cm/y. The evidence for episodic creep in the Cholame section of the SAF south-east of Parkfield is in contrast with previously published interpretations of GPS and trilateration data. The Cholame section of the SAF merits close monitoring because it was likely the nucleation site of the 1857 Fort Tejón earthquake and because it has shown recent evidence of deep slow slip as revealed by deep tremors

The Virtual Seismologist in SeisComP3: A New Implementation Strategy for Earthquake Early Warning Algorithms

The feasibility of earthquake early warning (EEW) is now widely recognized. However, EEW systems that are in operation or under evaluation worldwide have significant variations and are usually operated independently of routine earthquake monitoring. We introduce a software that allows testing and evaluation of a well‐known EEW algorithm directly within a widely used earthquake monitoring software platform. In the long term, we envision this approach can lead to (1) an easier transition from prototype to production type EEW implementations, (2) a natural and seamless evolution from very fast EEW source parameter estimates with typically large uncertainties to more delayed but more precise estimates using more traditional analysis methods, and (3) the capability of seismic networks to evaluate the readiness of their network for EEW, and to implement EEW, without having to invest in and maintain separate, independent software systems. Using the Virtual Seismologist (VS), a popular EEW algorithm that has been tested in real time in California since 2008, we demonstrate how our approach can be realized within the widely used monitoring platform SeisComP3. Because this software suite is already in production at many seismic networks worldwide, we have been able to test the new VS implementation across a wide variety of tectonic settings and network infrastructures. Using mainly real‐time performance, we analyze over 3200 events with magnitudes between 2.0 and 6.8 and show that, for shallow crustal seismicity, 68% of the first VS magnitude estimates are within ±0.5 magnitude units of the final reported magnitude. We further demonstrate the very significant effect of data communication strategies on final alert times. Using a Monte Carlo simulation approach, we then model the best possible alert times for optimally configured EEW systems and show that, for events within the dense parts of each of the seven test networks, effective warnings could be issued for magnitudes as small as M 5.0

Speciale: Il terremoto ligure del 23 Febbraio del 1887

L'educazione e la formazione sono due ingredienti che consentono ai cittadini di apprendere le informazioni scientifiche altrimenti confinate nei laboratori in particolare nel campo del rischio ambientale. E in questa ottica che è nato il programma O3E (acronimo in francese di Osservazione dell'Ambiente a scopo Educativo per le Scuole). II programma O3E fa seguito a un periodo di sperimentazione di 10 anni (1997-2007) in cui sono nati diversi progetti nazionali (Sismos a l'Ecole, EDURISK, climAtscope). L'obiettivo generale del programma O3E è mettere in rete istituti scolastici nelle regioni delle Alpi latine equipaggiate con sensori di parametri ambientali di tipo educativo. I dati sul movimento del suolo (sismometri), sulle temperature e la pluviometria (stazioni meteo), sulle risorse idriche (idrogeologia) registrati negli istituti scolastici sono raccolti su server dedicati poi messi a disposizione attraverso Internet alla comunità educativa. La rete O3E così strutturata, diventa il punto di partenza per varie attività di insegnamento delle geoscienze e di educazione al rischio naturale e si propone di: - promuovere le scienze sperimentali e le nuove tecnologie - mettere in rete gli attori dell'educazione e della formazione - sviluppare il senso di autonomia e la responsabilità dei giovani - rafforzare e sviluppare i legami con i partner regionali nel campo educativo e universitario - favorire una presa di coscienza razionale dei problemi legati alla prevenzione dei rischi naturali e del patrimonio geologico, ciò che può fare la differenza durante un evento in termini di sicurezza. Tenendo conto degli orientamenti del programma, che dà un grande spazio alle tecnologie di comunicazione, della sua dimensione educativa (sensibilizzazione ai rischi ambientali), del suo contenuto scientifico (geoscienze), e della sua importanza su scala regionale e persino internazionale (messa in rete di istituti scolastici), vengono avviate iniziative da parte degli istituti scolastici in stretta collaborazione con il mondo dell'Università e della Ricerca. E' il caso del presente opuscolo che tratta il caso di un terremoto emblematico per le regioni interessate da O3E: il terremoto di Imperia - Mentone del 23 febbraio 1887. I dati raccolti qui (archivi, sismogrammi, ultimi studi oceanografici. .. ) consentiranno agli studenti e ai loro insegnanti di affrontare un caso di studio.CG06, Region PACA, DIREN PACA, Sciences a l'Ecole; ALCOTRAPublished5.9. Formazione e informazioneope

Earthquakes, The hows and whys. Focus on The February 23, 1887 Ligurian earthquake

Education and training are two ingredients that allow citizens to learn scientific information otherwise confined within laboratories, in particular in the field of environmental risk. It is in this perspective that the O3E (French acronym for European Observatory for Education and Environment) project was born. The O3E project is the follow up of a 10 year long testing phase (1997-2007) during which several national projects ("Sismos a I'Ecole", "EDURISK" and "climAtscope") were born. The overall objective of the O3E program is to network educational institutions, which are equipped with educational instruments and sensors to measure environmental parameters, across regions of the Latin Alps. Data on ground motion (seismometers), temperatures and rainfall (weather stations), on water resources (hydrogeology) recorded in schools are collected on dedicated servers, which are then made available to the educational community through the Internet. The so-structured O3E network becomes the starting point for many geosciences teaching and educational activities to natural hazards in order to: - promote experimental sciences and new technologies - network the actors involved in education and training - develope the sense of autonomy and responsibility in young people - strenghten and develope relations with regional partners in the field of education and academia - foster rational awareness of the problems related to the geological heritage and to the prevention of natural hazards, that is what can make the difference, in terms of safety, when an event occurs. Taking into account the guidelines of the program (which gives a large space to communication technologies), its educational dimension (awareness of environmental risks), its scientific content (geosciences), and its importance on a regional and even international scale (networking of schools), initiatives are started up by schools in close cooperation with the university and research community. As it is the case of this pamphlet dealing with an earthquake, which is emblematic for the regions involved in the O3E project: the Imperia -Menton earthquake occurred on February 23,1887. The data collected here (archives, seismograms, recent oceanographic studies ... ) will enable students and their teachers to deal with a case study.CG 06, Région PACA, DIREN PACA, Sciences à l'Ecole; Alcotra, EUPublished5.9. Formazione e informazioneope

Earthquakes, The hows and whys. Focus on The February 23, 1887 Ligurian earthquake

Education and training are two ingredients that allow citizens to learn scientific information otherwise confined within laboratories, in particular in the field of environmental risk. It is in this perspective that the O3E (French acronym for European Observatory for Education and Environment) project was born. The O3E project is the follow up of a 10 year long testing phase (1997-2007) during which several national projects ("Sismos a I'Ecole", "EDURISK" and "climAtscope") were born. The overall objective of the O3E program is to network educational institutions, which are equipped with educational instruments and sensors to measure environmental parameters, across regions of the Latin Alps. Data on ground motion (seismometers), temperatures and rainfall (weather stations), on water resources (hydrogeology) recorded in schools are collected on dedicated servers, which are then made available to the educational community through the Internet. The so-structured O3E network becomes the starting point for many geosciences teaching and educational activities to natural hazards in order to: - promote experimental sciences and new technologies - network the actors involved in education and training - develope the sense of autonomy and responsibility in young people - strenghten and develope relations with regional partners in the field of education and academia - foster rational awareness of the problems related to the geological heritage and to the prevention of natural hazards, that is what can make the difference, in terms of safety, when an event occurs. Taking into account the guidelines of the program (which gives a large space to communication technologies), its educational dimension (awareness of environmental risks), its scientific content (geosciences), and its importance on a regional and even international scale (networking of schools), initiatives are started up by schools in close cooperation with the university and research community. As it is the case of this pamphlet dealing with an earthquake, which is emblematic for the regions involved in the O3E project: the Imperia -Menton earthquake occurred on February 23,1887. The data collected here (archives, seismograms, recent oceanographic studies ... ) will enable students and their teachers to deal with a case study