Western Greece (Kefalonia) earthquakes: Mw 6.1 and Mw 6.1 on January 26 and February 3, 2014

A second earthquake of Magnitude Mw 6.1 occurred in the same area on February 3.

03 Feb., 2014, 10h30 (Fr): Comment: focal mechanisms for this second choc vary, but the dominant tendency among them is like the first shock of January 26th, i.e. strike-slip, with a nodal plane NNE-SSW right-lateral (B.Delouis).

Date and location from EMSC:

in the same area on February 3.

Additional mechanism for the Feb 3 Mainshock from FMNEAR (B.Delouis) running at NOA:

03 Feb, 17h30 (Fr). Posted by Jean-Claude Ruegg. Simulation of ground displacements produced by the second choc (Mw 6.0 - 6.1).

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Information about ongoing actions:

Jan. 27th, 11h08 (Fr): Lucia Margheriti (INGV) contacted colleagues in charge of rapid response of the NERA project (Europ), and Nicos Melis of the Athens Observatory. Waiting for answers, to know if a unified action is undertaken.

Jan. 27th, 11h50 (Fr), information provided by Pierre Briole (ENS):

It is thought to measure again a set of GPS points measured in 2010 in the area. Pierre and 3 other colleagues (Panagiotis, Alex, Nikos Roukounakis) will arrive in Patras on wednersday afternoon and will see with greek colleagues (Stathis, Sotiris and Fanis ) what actions to take. These colleagues already calculated some preleminary GPS displacement at a point in Kephalonia.

Jan. 27th, 12h55 (Fr), information provided by Yann Klinger (IPGP). Colleagues of INGV would be interesed in a joint French - Italian field trip.

Jan. 27th, 15h40 (Fr). information provided by Cecile Cornou:

Today there is a small group from NOA (Athens Observatory) on the go, who will deploy by tomorrow 4 more seismic stations on the island. Other european teams may contact Nicos Melis, join his group, and have a support from him.

Jan. 27th., 17h20 (Fr). Up to now, no european groups (outside Greece) have decided to go to the field for seismology, at least to my knowledge (Bertrand Delouis).

Jan. 28th., 14h45 (Fr). Information given by Pierre-Yves Bard (Isterre) on Jan. 26th.

The site of Argostoli-Koutavos (in Kefalonia) is a test-site for the NERA european project and the french ANR-PIA project (P.I. Catherine Berge-Thierry) for studying the spacial variability, 3D aspects, and non linearity of site effects. The group involved in these projects, including the french LDG, CEA - Cadarache, IRSN, CEREMA) is evaluating the possibility to organize a campaign to measure the aftershocks of the Jan. 26th (Mw 6.1) earthquake. To date, 20-25 CMG6TD (CEA Cadarache + IRSN) + a few strong motion stations (CEREMA Nice) have been identified for such campaign. A few colleagues from CEA Cadarache, LDG, and maybe IRSN could go to the field. The contact person in Greece is Nikos Theodoulidis.

Jan 28th., 17h20 (Fr). Information given by Pierre-Yves Bard.

In addition to the material described above, a request was made to the French national pool of mobile seismological stations (SISMOB): 5 strong-motion stations and 5 broad-band (CMG-40) stations. In contact with L. Margheriti, G. Cultrera at INGV for possibly a joint action. INGV would bring 6 additional stations. Coordinated in Greece with l'ITSAK Thessalonique (N. Theodoulidis), who already installed two additional strong-motion stations and 4 velocimeters in the island, and locally with A. Konidaris, TEI Argostoli. The local authorities have been contacted also.

The french mission should go to the field at the end of the week, under the leadership of Fabrice Hollender (CEA). It will include V. Perron (PhD student), + colleagues from LDG, IRSN et Centrale Paris. The mission will be founded by the projects (NERA, ANR-PIA). In addition to the classical strong-motion and broad-band stations, a rotation sensor from ISTERRE will be tested.

Jan. 29th, 17 - 19h: posted by Giovanna Cultrera and Lucia Margheriti (INGV):

INGV decided to install 6 stations in Kefalonia to record aftershocks of the M>6 earthquake in the framework of the site response studies started in 2011 (principal investigator for NERA group is P.Y Bard).

People from INGV (which were already in Kefalonia for the 2011-2012 experiment) will arrive to Argostoli on Sunday 2nd or Monday 3rd

and install the 6 Quanterra 6 channels (equipped with Le-5s and Episensor). The idea is tu put the stations on the same location of the previous experiment and leave them for about 1 month, details and coordinations are under discussion inside the site response working group.

We know also French are going in the same days to install seismic stations.

Hopefully all the data will be archived in Eida (restrictions will be applied to the data) so all of us should help in getting smooth procedures to archive data and in making sure all the participants of different nationality can exchange data trough EIDA.

In the klm file you can find their position with the value of the measured resonance frequency: Ker02, centre of Array B, centre of Array A, Keg01 (or south of it), Kes20-Police station; the last one could be installed at the University or Kes14-15 or Array E-F (yellow symbols in the map). In attach the file with the resonance frequencies from previous experiments.

Jan. 30th, 10h51 (Fr). Posted by Nicos Melis (NOA):

NOA has at the moment in operation the following stations on Cephalonia Island:

Portable

KEF1 38.2778 20.4709 0 Digitiser: Geoinstruments Smart24 Seismometer: Lennartz 3D-20sec

KEF2 38.1654 20.4870 150 Digitiser: Geoinstruments Smart24 Seismometer: Lennartz 3D-20sec

KEF3 38.2031 20.3482 115 Digitiser: Geoinstruments Smart24 Seismometer: Lennartz 3D-20sec

KEF4 38.2580 20.4244 41 Digitiser: Geoinstruments Smart24 Seismometer: Lennartz 3D-20sec

Permanent

VLS 38.1768 20.5886 402 Digitiser: Geoinstruments Plc DR-24 Seismometer: Trillium 120P

Accelerographs

LXRB 38.2010 20.4374 5 A-800 Triggered Mode

ARGA 38.1770 20.4789 6 A-800 Triggered Mode

SMHA 38.2512 20.6477 5 CMG-5TD Continuous Mode

Regarding EIDA, NOA is not yet part of the Consortium. We are working towards this and through NERA we aim to join.

Data are archived at NOA via seedlink, hence Arclink, apart from the two in triggered mode accelerographs.

It would be good to know who will be involved in this "expedition" and of course to decide regarding the use of the data that will be collected via this "expedition".

Jan. 30th, 22h (Fr). Posted by Fabrice Hollender (CEA):

On our side, we will be 7 (see attached file the name and phone number), arriving on Sunday evening. 5 of us by plane, 2 by car (and ferries…) with all the material. Will stay up to 5 days (some of us will leave before).

We will split into two teams.

The first one (that I will lead) will install 21 seismometers (CMG6TD) on a rock site with a geometry close from the NERA array A. See in attached file the area (this is not the exact geometry but the area is the right one). These sensors will stay here for one month.

The second team (leads by Sebastien Hok) will install 2 rotation sensors + 5 accelerometers in Koutavos area. The exact positions are not definitively defined, but one can suggest to install one on the reference site near the pumping station (this will double your position, but it could be worth to ensure the “reference” solution). Other have to be place in Koutavos park on different possible location of future borehole (the exact position is not fixed, and so, the experiment may also be seen as a “validation” for the borehole location). We can make a "scouting” on Monday and wait on the INGV team to decide in coordination.

The french team going to the field:

Fabrice HOLLENDER: +33 6 84 01 28 68

Vincent PERRON: +33 6 84 44 50 60

Marc CUSHING: +33 6 08 65 81 35 // +33 6 78 88 60 89

Sébastien HOK: +33 6 15 54 31 34

Aurore LAURENDEAU: +33 6 82 45 74 28.

Angkeara SVAY: +33 6 69 20 11 03

Régis COTTEREAU

Jan. 30, 23h30 (Fr). Posted by Pierre-Yves Bard (ISTerre).

This specific experiment will include the following items

· iiinstallation of a small-aperture, dense array on rock in a non-cultivated field area located to the South-East of the Koutavos Park, with the agreement of the private land owners (21 stations approximately, maximum 200 m aperture). The duration of this experiment will be between 4 and 6 weeks. The (tentative) coordinates of this small aperture array are indicated in the attached kHz file. The objective is to investigate the small scale spatial variability of ground motion on rock - extending what had been done in NERA on the soft sediments in Koutavos park.

Installation in and around the Koutavos Park of 2 rotation sensors and 5 accellerometers to investigate the non-linear and rotational response of the area (to be compared with the linear response obtained during the NERA experiment in 2011-2012), together with the installation of a reference station in the water pumping station. This duration of this experiment will be at least 5-6 weeks. This will be done in close discussion with the INGV team, phone exchanges were already organized to harmonize the two experiments.

This is indeed a follow-up of the collaboration initiated within the NERA-JRA1/JRA3 project, focusing on the 3D seismic response of the Argostoli-Koutavos area. Considering the very high level of seismic activity in the Ionian sea, it had been decided in 2012 to propose a new project within the French ANR funding environment, in order to establish in Argostoli a test site for investigations on the non-linear response of small size, shallow, 3D alluvial basins. This project was finally funded in 2013 as the "SINAPS@" project, coordinated by CEA, and gathering a total of 11 partners (EDF, ENS, ECP, 3SR, ISTerre, IFSTTAR, CEREMA, ECN, EGIS, AREVA) with the contribution of ITSAK-EPPO. Since the NERA project is almost over, most of the funding is coming from this SINAPS@ project and from an older one names CASHIMA.

Within these two projects (and NERA as well), the experiments in Argostoli are organized in very close collaboration with ITSAK-EPPO Thessaloniki : this will be the case also for this emergency action following the January 26 event.

Feb., 2, 2014, 12h (Fr). Posted by Cecile Cornou, information given by Giovanna Cultrera (INGV):

Location of stations that will be installed by the INGV:

station at the University, as follow:

sta1 KER02 38.16627454 20.51049392

sta2 KEB01 38.16548164 20.50801377

sta3 KEA00 38.16331671 20.50554879

sta4 (sta5-3 in mappa) University 38.168776 20.496338

sta 5 - 1 KES13 38.16334788 20.50399188

sta 5 - 2 KES14 38.16388002 20.50219485

sta6 KES20 38.16312 20.49746

The INGV people (Gaetano, Rocco and Stefania, in cc.) will arrive on Monday around 17. Their phone numbers are:

Gaetano +39 3395493786

Rocco +39 3289570961

If you need to discuss with me while you are there, you can reach me either by e-mail or Skype, or by phone (+39 3492339956).

Ciao et bon voyage

Giovanna

Feb. 3, 2014, 17h20 (Fr). Message from F. Hollender (CEA).

Today, we installed 1 accelerometer on the reference site (near pumping station) + 1 accelerometer + rotation sensor near the center of the Array A. Since it is very important positions, it seems to us usefull to double measurements on these sites.

We will put our 3 other accelerometers in the Koutavos site at place do be discussed with Nikos and you collegues (note that when I talked about the "borehole", I was talking about the future borehole we plan to drill inside the Koutavos site, not the one located on the other side of the raod).

Feb. 4, 2014, 16h50. Posted by Fabrice Hollender (CEA, leader of the french field team):

De notre côté, "petite" journée : quelques difficultés d'accès à notre "base logistique" (IUT d'Argostoli qui accueille aussi le centre de crise) compte tenu de la vistes de ministres... et des trombes d'eau. Nous n'avons pu mettre en place que 2 (!) capteurs, mais j'espère qu'après quelques ajustements de procédure de mise en place (essentiellement pour nous protéger et protéger le matériel sur le terrain), nous allons pouvoir avancer demain (même si le temps est toujours à la pluie).

Feb. 13, 2014. Posted by Fabrice Hollender. Seismic stations (including dense array) installed by the French team:

Feb 13, 2014. Poster by Giovanna Cultrera. Seismic stations installed by the INGV (may stay for one month):

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Information about the January 26th, Mw 6.1 earthquake (first choc):

Mainshock followed by several aftershocks of M > 4. The mainshock is in strike-slip, but one of the largest aftershock (Jan. 26, 18h45 UTC, Mw 5.4) is reverse (striking North-South).

Date and location from EMSC:

Focal mechanism and depth of the mainshock (from different agencies, compiled by EMSC):

Jan. 27th, 12h01 (Fr): Synthetic SAR interferogram for the mainshock, posted by Pierre Briole (ENS). (Descending, C band) simulated with a fault whose top is located 2km below the surface.

Jan. 28th. 15h (Fr). Posted by Jean-Claude Ruegg on Jan. 26th.

Link towards the theoretical ground displacements produced by the mainshock:

http://www.geologie.ens.fr/spiplabocnrs/seismes/Greece%20Mw=6.10.htm

Aftershock of Jan 26th, 18h45 UTC Mw 5.4 showing reverse faulting (compiled by EMSC):

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Geological, tectonic, geodynamic setting:

Jan. 27th, 15h30. See the attached articles on the area (below), posted by Mireille Laigle (Géoazur)