Wide-angle seismicsea-land acquisition a

A Ger asi1 2 I G erra2 R L Festa2 R de Franco3 G C

Istituto per la Dinamica dei processi ambientali

Gruppo Nazionale di Geofisica della Terra Solida 34

IntroductionThe main objective of the CHIANTI-1 cruise (Calabrian Arc Hazards in IoniAN andTyrrhenIan Seas is to collect several transects of deep penetrating wide angle seismic(WAS) data, together with sediment profiler and multi-beam bathymetry data, across theIonian and Tyrrhenian seas to determine the deep crustal structure and plate geometry ofthe whole subduction system from the frontal wedge to the arc and back arc The goal is

A. Gervasi1, 2, I. Guerra2, R.L. Festa2, R. de Franco3, G. CB. M. Ligi 5, I.

1Istituto Nazionale di Geofisica e Vulcanologia, INGV-CNT, Rome, Italy; 2Dipartimento di Biologia, Ecologia e ScienItaly; 4Consejo Superior de Investigaciones Científicas - Institut de Ciències del Mar (CSIC-ICM), Barcellona, Spai

the whole subduction system, from the frontal wedge to the arc and back-arc. The goal isto study the processes that operated during the subduction of the Ionian slab of oceaniccrust under Calabria, which lead to the development of the Aeolian volcanic arc, and thesubsequent opening of the Tyrrhenian basin, and are responsible of the geologicalhazards that threaten the region. In addition, the data acquired will allow us to improvethe knowledge on the interrelationships between tectonics and magmatism to define themost significant geological hazards, including large earthquakes, tsunamis, submarinelandslides, and volcanic eruptions.The data were collected using a temporary network deployed for few days (from 21 to 31July, 2015) on the sea floor, with a series of Ocean Bottom Seismometers andHydrophones (OBS/OBH). The experiment also included the on land recording withpermanent and temporary seismic stations managed and deployed by Calabria University(UniCal). The temporary seismic stations were located along the transect FrancavillaAngitola – Montepaone The project will benefit from data observed at the stations of the

a)

b)

c)

Angitola Montepaone. The project will benefit from data observed at the stations of theItalian National Seismic Network of INGV.The source of energy to acquire the data was an array of airguns with a total capacity of~4750 c.i. The explored wide-angle seismic (WAS) transects were located both in Ionianand Tyrrhenian seas. During the cruise were followed all necessary measures to minimizeunderwater acoustic impact on marine life. Measures include continuous monitoring of theresearch activities by a team of three Marine Mammal Observers (MMOs) which used bothvisual and Passive Acoustic Monitoring (PAM) systems.Here we present the preliminary results (pre-processing) of the data recorded by the on-land temporary stations. The sea-land data will be later processed and integrated withOBS/H-WAS data and interpreted together with multichannel data, in order to constructmodels of the tectonic features and the seismic velocity structures of the crust and uppermantle.

Float of airgun sub-array after deployment

Airgun configuration of the CHIANTI-1 seismic source. The size of thesquares in the blue grid is 1x1 m.

Vessel Sarmiento de Gamboa (CSIC) MCS data andWARR Shooting.

Multi-channel reflection (MCS) and wide-angle reflection/refraction seismic data were acquired

MCS data were acquired in common shot gather from 3450 m streamer (276 ch), shot spacing

WARR data were acquired in common receiver gather from OBH, OBS, on-land stations; 90 s s

Data recorded on landStarting from July 21st, three temporary, continuously recording seismic stations were installedWAS2 profiles. All of them were equipped with Guralp CMG40T broadband sensors and data-UMTS/GPRS to the recording center at the UniCal Campus, while the last two recorded data on lpoints resulted in about 10 km. The westernmost station UC01 at Francavilla Angitola is still opJuly 31st.In the panels in the first row below, record sections (Z components) of temporary UniCal station

UC05UC03UC01

WAS1

normal and reduced times, together the bathymetry. Their interpretation is underway. In the supermanent INGV stations CET2 (fan arrangement), JOPP and PLAC, where high quality data hamore possible permanent peri-tyrrhenian stations has been scheduled.

WAS2

CET2 JOPP

Record section of OBS35 along WAS3 (vertical component)

Examples of OBS records

Record section of OBS19

c CHIANTI-1 project:nd preliminary results

Caielli3 A Corsi3 V Sallares4 C R Ranero 4 N Zitellini5

4° CONVEGNO TRIESTE 17-19 Novembre 2015

Dipartimento di Biologia, Ecologia e Scienze della Terra

Caielli3, A. Corsi3, V. Sallares4, C.R. Ranero 4, N. Zitellini5, Grevemeyer6

nze della Terra, Arcavacata, Italy; 3IDPA Institute for the Dynamics of Environmental Processes (CNR), Milan, n; 5ISMAR - Istituto Scienze Marine (CNR), Bologna, Italy 6IFM-GEOMAR, Kiel, Germany.

Acquisition layout

a)

b)

b)Bathymetric map of the study area with the WAStransects, labeled WAS1 to WAS4 (red lines). Yellow circleslabeled OBS01 to OBS49 indicate the OBS location alongWAS1, WAS2 and WAS3 profiles. Red circles labeledOBS05 to OBS67 indicate OBH location along the WAS4profile.

Seismic stations operating in Calabria and adiacentregions. Red triangles: INGV/CNT stations; green: UniCalpermanent stations; blue: UniCal temporary stations(eastward from the West: UC01, UC03 and UC05).

Coloured relief map of profiles WAS1 and WAS2 acquiredduring Leg 2.

c)b)

Signature of thr source wavelet used during theCHIANTI-1 wide-angle seismic cruise

-e Ocean Bottom Hydrophone

(OBH)Ocean Bottom Seismometer

(OBS)

shooting twice the same lines using different devices, geometry and acquisition parameters.

50 m, fold 35, source 9 G-II airguns 3040 inch3

hoting interval, ~220 m shot spacing, source two arrays of 9 G-II airguns, 4750 inch3.

( )

UC01 seismic stationat Francavilla A. (VV).d by UniCal on the transect joining the WAS1 and

-loggers Reftek-72A. The first one was linked viaocal HD. The distance between adjacent recording

perating while the other ones were deactivated on

ns on the on-land transect are represented both in

UC05UC03UC01

WAS2

ccessive one, we report the record sections of theave been recorded. The utilization of data from as

PLAC

along WAS2 (vertical component) Record section of OBS17 along WAS1 (vertical component)