Philippe Charvis
The Ecuador-Colombia subduction zone has been affected over the last century by a remarkable sequence of large earthquakes. This earthquake supercycle started with the great 1906 Mw 8.5-8.8 earthquake, which ruptured a 500-km-long segment of the subduction megathrust from northern Ecuador to Colombia. A sequence of three large earthquakes with Mw from 7.7 to 8.2 re-broke several sub-segments of the same area in 1942, 1958 and finally in 1979, cascading progressively from south to north along the subduction zone [Mendoza and Dewey, 1984]. In April 2016, the Mw 7.8 Pedernales earthquake broke again the zone that had ruptured 74 years earlier in 1942 [Nocquet et al., 2016], possibly starting a new cascade of earthquakes. The 2016 event killed more than 650 people, producing 30 000 casualties and major damages to the country (the economic loss and the cost for recovery and reconstruction are estimated in $3.3 billions, ~3% of the Growth Domestic Product of the Country).
The primary objective of the PhD project is to understand which conditions (properties of the subduction zone, stress accumulation, etc.) induced this remarkable sequence of large earthquakes. Such understanding is critical, not only to better assess seismic hazard related to the South America subduction zone, but also to better understand how large earthquakes cycle along faults to break them entirely and repeatedly.
Immediately after the earthquake, we deployed an onshore-offshore network of ~80 seismometers within the affected zone, in the framework of an international cooperation between scientists from Ecuador, France, UK and USA. The deployed network was dedicated to reinforce the existing permanent network so as to accurately record the aftershock sequence (precise location, magnitude, fault regime, etc) over a one-year period. The first analyses of the recorded data show that the fault zone ruptured by the Pedernales earthquake is approximately 100 km long and 50 km wide [Nocquet et al., 2016]. However, the region of the fault that is sustaining postseismic deformation since the earthquake is much larger, about 200 km long and 100 km wide, as revealed by the preliminary aftershock locations. The post-seismic period has included so far several large aftershocks (Mw ~6) and several slow slip earthquakes.
This PhD work is devoted to analyze the available seismic data (from the temporary and the permanent seismic networks), and use the results to better understand how the recent earthquake is related to the prior large events on the same zone. The results will then be used to investigate the hypothesis that the Pedernales earthquake might be the beginning of a new cascade of earthquakes similar to the 1942-1979 sequence, assessing the implications of this to the re-evaluation of the seismic hazard in northern Ecuador.
The candidate will thus need to conduct seismological analyses of land and ocean bottom seismograms, including picking of seismic wave arrival times and waveform analyses including waveform match techniques and moment tensor inversion. Some experience with the use of Linux systems, and of Shell, Matlab, and/or Python programing will be appreciated. The candidate will have to travel to Ecuador at a few times in order to collaborate with our Ecuadorian partners. Similar trips to Liverpool and the US are likely.
The position will open in September 2017 and the student will be based at Géoazur laboratory, next to Nice. The application should be addressed to Dr. Philippe Charvis (philippe.charvis-at-geoazur.unice.fr) and should include CV, names of references, motivation letter, including specific interests and prior experience in areas related to the project.
National and international context:
This PhD project is in the framework of the ongoing REMAKE ANR project (ANR-15-CE04-004 REMAKE, P.I. Ph. Charvis) and of the Joint International Laboratory (LMI-SVAN Sismos y Volcanes en los Andes del Norte) between the Instituto Geofísico de la Escuela Politécnica Nacional (http://www.epn.edu.ec/events/sismos-y-volcanes-en-los-andes-del-norte/) and the French National Research Institute for sustainable development (http://www.ird.fr/la-recherche/lmi-laboratoires-mixtes-internationaux/lmi-svan-seismes-et-volcans-dans-les-andes-du-nord).
The data acquisition has been conducted in the framework of an international cooperation involving Géoazur (Nice) and ISTerre (Grenoble) laboratories, the Instituto Geofísico - Escuela Politécnica Nacional (IG-EPN), the Department of Earth and Environmental Sciences, Lehigh University (LU), the Department of Geosciences, University of Arizona (UAZ) and the Department of Earth, Ocean and Ecology, University of Liverpool (ULP). Collaborators belong to these different institutions: Hans Agurto Detzel, Audrey Galve, Boris Marcaillou, Yvonne Font, Marc Régnier, Jean-Mathieu Nocquet (Géoazur), Monica Segovia, Sandro Vaca (IG-EPN), Andreas Rietbrock (ULP), Anne Meltzer (LU), Susan Beck (UA)
References
Mendoza, C., and J. W. Dewey (1984), Seismicity associated with the great Colombia-Ecuador earthquakes of 1942, 1958 and 1979: implications for barrier models of earthquake rupture, Bull. Seismol. Soc. Am., 74(2), 577–593.
Nocquet, J.-M. et al. (2016), Supercycle at the Ecuadorian subduction zone revealed after the 2016 Pedernales earthquake, Nat. Geosci., 1(December), doi:10.1038/ngeo2864.
The primary objective of the PhD project is to understand which conditions (properties of the subduction zone, stress accumulation, etc.) induced this remarkable sequence of large earthquakes. Such understanding is critical, not only to better assess seismic hazard related to the South America subduction zone, but also to better understand how large earthquakes cycle along faults to break them entirely and repeatedly.
Immediately after the earthquake, we deployed an onshore-offshore network of ~80 seismometers within the affected zone, in the framework of an international cooperation between scientists from Ecuador, France, UK and USA. The deployed network was dedicated to reinforce the existing permanent network so as to accurately record the aftershock sequence (precise location, magnitude, fault regime, etc) over a one-year period. The first analyses of the recorded data show that the fault zone ruptured by the Pedernales earthquake is approximately 100 km long and 50 km wide [Nocquet et al., 2016]. However, the region of the fault that is sustaining postseismic deformation since the earthquake is much larger, about 200 km long and 100 km wide, as revealed by the preliminary aftershock locations. The post-seismic period has included so far several large aftershocks (Mw ~6) and several slow slip earthquakes.
This PhD work is devoted to analyze the available seismic data (from the temporary and the permanent seismic networks), and use the results to better understand how the recent earthquake is related to the prior large events on the same zone. The results will then be used to investigate the hypothesis that the Pedernales earthquake might be the beginning of a new cascade of earthquakes similar to the 1942-1979 sequence, assessing the implications of this to the re-evaluation of the seismic hazard in northern Ecuador.
The candidate will thus need to conduct seismological analyses of land and ocean bottom seismograms, including picking of seismic wave arrival times and waveform analyses including waveform match techniques and moment tensor inversion. Some experience with the use of Linux systems, and of Shell, Matlab, and/or Python programing will be appreciated. The candidate will have to travel to Ecuador at a few times in order to collaborate with our Ecuadorian partners. Similar trips to Liverpool and the US are likely.
The position will open in September 2017 and the student will be based at Géoazur laboratory, next to Nice. The application should be addressed to Dr. Philippe Charvis (philippe.charvis-at-geoazur.unice.fr) and should include CV, names of references, motivation letter, including specific interests and prior experience in areas related to the project.
National and international context:
This PhD project is in the framework of the ongoing REMAKE ANR project (ANR-15-CE04-004 REMAKE, P.I. Ph. Charvis) and of the Joint International Laboratory (LMI-SVAN Sismos y Volcanes en los Andes del Norte) between the Instituto Geofísico de la Escuela Politécnica Nacional (http://www.epn.edu.ec/events/sismos-y-volcanes-en-los-andes-del-norte/) and the French National Research Institute for sustainable development (http://www.ird.fr/la-recherche/lmi-laboratoires-mixtes-internationaux/lmi-svan-seismes-et-volcans-dans-les-andes-du-nord).
The data acquisition has been conducted in the framework of an international cooperation involving Géoazur (Nice) and ISTerre (Grenoble) laboratories, the Instituto Geofísico - Escuela Politécnica Nacional (IG-EPN), the Department of Earth and Environmental Sciences, Lehigh University (LU), the Department of Geosciences, University of Arizona (UAZ) and the Department of Earth, Ocean and Ecology, University of Liverpool (ULP). Collaborators belong to these different institutions: Hans Agurto Detzel, Audrey Galve, Boris Marcaillou, Yvonne Font, Marc Régnier, Jean-Mathieu Nocquet (Géoazur), Monica Segovia, Sandro Vaca (IG-EPN), Andreas Rietbrock (ULP), Anne Meltzer (LU), Susan Beck (UA)
References
Mendoza, C., and J. W. Dewey (1984), Seismicity associated with the great Colombia-Ecuador earthquakes of 1942, 1958 and 1979: implications for barrier models of earthquake rupture, Bull. Seismol. Soc. Am., 74(2), 577–593.
Nocquet, J.-M. et al. (2016), Supercycle at the Ecuadorian subduction zone revealed after the 2016 Pedernales earthquake, Nat. Geosci., 1(December), doi:10.1038/ngeo2864.
