ALBERT

Description: Acoustic direct line-of-sight distance measurements offshore Etna volcano by means of a network of five transponders. The data include travel times between all transponders, pressure, temperature (inside pressure tube), sound velocity, and inclination.

Description: Multibeam echosounder (MBES) data recorded during RV METEOR cruise M111 between 10.10.2014 and 01.11.2014 in the eastern Mediterranean Sea. The aim of the cruise was to quantify the deep geometry and architecture of the Calabria subduction zone and Ionian Sea lithosphere and to shed light on the nature of the Ionian Sea with OBS/OBH and deep sea seismics. Additionally the M111 cruise formed the core of an ambitious investigation covering the Ionian Sea and island of Sicily. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval. Description of processed data sources: During the cruise M111 the Kongsberg EM122 multibeam echosounder with a nominal sounding frequency of 12 kHz was utilized. 288 beams (and up to 864 soundings in equidistant and dual swath mode) are formed for each ping with a 1°(Tx)/2°(Rx) footprint while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult https://www.km.kongsberg.com/. The EM122 was recording during the deployment of the OBH/OBS, during seismic surveys and during transits. Responsible person during this cruise / PI: Ingo Klaucke (iklaucke@geomar.de). Chief Scientist: H. Kopp hkopp@geomar.de CR: https://www.tib.eu/de/suchen/id/awi%3Adoi~10.2312%252Fcr_m111/ CSR: http://www.bsh.de/aktdat/dod/fahrtergebnis/2014/20140277.htm Responsible person for data delivery and approval: Paul Wintersteller (seafloor-imaging@marum.de) A special thanks goes to to the watch keeper during M111: Marzia Rovere, Ingo Klaucke, Anne Krabbenhoeft, Marc-André Gutscher

Description: During RV Meteor cruise M111 refraction and wide-angle reflection seismic data were acquired. We present eight seismic record sections (.sgy format) of the hydrophone components from four ocean bottom hydrophones (OBH501, OBH503, OBH505, OBH507) and four ocean bottom seismometers (OBS502, OBS504, OBS506, OBS508) along the NNE-SSW oriented seismic profile DY-05, which is situated in the Ionian Abyssal Plain. The profile stretches over a distance of 131 km and was shot using an airgun array of six G-gun clusters with a total volume of 84 l (5440 cu in) at 210 bar. A total of 946 shots were fired every 60 s (~140 m) with an airgun towed behind the vessel in a depth of 8 m. Data are unprocessed, however, they are corrected for instrument drift along the profile using the symmetry of the direct arrival and the data are time corrected.

Description: The backscatter data were collected during R/V SONNE Cruise SO244. For processing of the backscatter information, all data recorded during turns of the ship were eliminated before gridding to a 20 m cell size throughout the study area.

Description: The submerged North Anatolian Fault in the Sea of Marmara is lacking any major seismic activity since its last rupture in 1766. The purpose of this acoustic ranging experiment was to determine whether this fault is continuously and aseismically creeping (i.e. slipping) or whether it is locked and thus accumulating stress that could cause a large magnitude earthquake, few tens of kilometers away from Istanbul. In October 2014, a ranging network of 10 acoustic transponders was installed across an active segment of the North-Anatolian Fault in the Marmara Sea at a depth of about 800 m (Figures 1 and 2, see further details). Figure 1: Map showing the location of the geodetic network in the Sea of Marmara (yellow box). Local ocean bottom seismometer (OBS) stations (29/10/2014-25/04/2015 and 26/04/2015-13/04/2016) are indicated with black triangles. Bathymetry in the central Sea of Marmara from Le Pichon et al. (2001) (https://doi.org/10.1016/S0012-821X(01)00449-6) and topography from Ryan et al. (2009) (https://doi.org/10.1029/2008GC002332). Figure 2: Map showing the location of the geodetic stations (red points indicate geodetic transponders from GEOMAR labelled with transponder IDs and green points indicate the French transponders). Bathymetry from AUV mapping (Grall et al. 2018, https://doi.org/10.17882/55744). Baselines of the intercommunicating transponders of Geomar shown with lines. The black baseline (G2302-G2307) has no line of sight. The long baselines with lengths of larger than 1000 m (shown in orange) are configured to work only unidirectional. White lines show bidirectional baselines. Figure taken from cruise report of POS484 (https://doi.org/10.3289/CR_POS_484/1). The acoustic network comprised 4 transponders from the University of Brest, France, and 6 transponders from GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany. The data available through this web site correspond to the data collected by the 6 German stations of GEOMAR's GeoSEA Array only. Data and details of the 4 French stations are accessible here: https://www.seanoe.org/data/00486/59750/ Data from the GeoSEA Array available here include sets of acoustic ranging between pairs of stations (i.e. two-way-travel times), in addition to sound-speed, temperature and pressure measurements at each station. Sample rate was 120 minutes during the 2.5 years of data availability. These are the raw, unprocessed data. For instance, distances must be inferred from two-way-travel times and sound-speeds. Deployment and data upload cruises: - Stations were installed during the MARSITE cruise, leg1 (from 28/10 to 01/11 2014) with RV Pourquoi Pas? (https://doi.org/10.17600/14000500). - First data download and visual inspection of the transponders with ROV were made during the MARSITE cruise, leg3 (13 to 16 November 2014). - In April 2015, the data were acoustically downloaded from the seafloor transponders using a modem from the sea surface during RV Poseidon cruise POS484 (https://doi.org/10.3289/CR_POS_484/1). - In April 2016, the data were again downloaded during RV Poseidon cruise POS497 (https://doi.org/10.3289/CR_POS_497). - In May 2017, a third set of acoustic ranging data was downloaded with RV Yunus (cruise YUNUS17). - In January 2018, a download was attempted with RV Yunus (cruise YUNUS18), but the German transponders did not respond, most likely due to empty batteries of the transponders on the seafloor. Three of the French instruments responded which had larger batteries, and two were retrieved from the seafloor because their batteries were almost exhausted. Details on the Sonardyne transponders and user manuals of the 6TD autonomous monitoring system can be found here: https://www.sonardyne.com/product/autonomous-monitoring-system/

Description: Multibeam bathymetric data were acquired during R/V SONNE Cruises SO104, SO244, and R/V Marcus G. Langseth Cruise MGL1610. The datasets were individually processed and gridded with grid cell sizes of 75 m. For the combined grid, depth information from SO244 was used wherever possible. If no SO244 data were available, MGL1610 data were preferred over SO104 data. The backscatter data were collected during R/V SONNE Cruise SO244. For processing of the backscatter information, all data recorded during turns of the ship were eliminated before gridding to a 20 m cell size throughout the study area.

Description: Multibeam bathymetric data were acquired during R/V SONNE Cruises SO104, SO244, and R/V Marcus G. Langseth Cruise MGL1610. The datasets were individually processed and gridded with grid cell sizes of 75 m. For the combined grid, depth information from SO244 was used wherever possible. If no SO244 data were available, MGL1610 data were preferred over SO104 data.

Description: In the Ionian Sea (central Mediterranean) the slow convergence between Africa and Eurasia results in the formation of a narrow subduction zone. The nature of the crust of the subducting plate remains debated and could represent the last remnants of the Neo-Tethys ocean. The origin of the Ionian basin is also under discussion, especially concerning the rifting mechanisms as the Malta Escarpment could represent a remnant of this opening. This subduction retreats toward the south-east (motion occurring since the last 35 Ma) but is confined to the narrow Ionian basin. A major lateral slab tear fault is required to accommodate the slab roll-back. This fault is thought to propagate along the eastern Sicily margin but its precise location remains controversial. This study focuses on the deep crustal structure of the eastern Sicily margin and the Malta Escarpment. We present two two-dimensional P wave velocity models obtained from forward modeling of wide-angle seismic data acquired onboard the R/V Meteor during the DIONYSUS cruise in 2014. The results image an oceanic crust within the Ionian basin as well as the deep structure of the Malta Escarpment, which presents characteristics of a transform margin. A deep and asymmetrical sedimentary basin is imaged south of the Messina strait and seems to have opened between the Calabrian and Peloritan continental terranes. The interpretation of the velocity models suggests that the tear fault is located east of the Malta Escarpment, along the Alfeo fault system. ©2018. American Geophysical Union. All Rights Reserved.

Description: The nature of the Ionian Sea crust has been the subject of scientific debate for more than 30 years, mainly because seismic imaging of the deep crust and upper mantle of the Ionian Abyssal Plain (IAP) has not been conclusive to date. The IAP is sandwiched between the Calabrian and Hellenic subduction zones in the central Mediterranean. A NNE–SSW-oriented 131 km long seismic refraction and wide-angle reflection profile, consisting of eight ocean bottom seismometers and hydrophones, was acquired in 2014. The profile was designed to univocally confirm the proposed oceanic nature of the IAP crust as a remnant of the Tethys and to confute its interpretation as a strongly thinned part of the African continental crust. A P-wave velocity model developed from travel-time forward modelling is refined by gravimetric data and synthetic modelling of the seismic data. A roughly 6–7 km thick crust with velocities ranging from 5.1 to 7.2 km s−1, top to bottom, can be traced throughout the IAP. In the vicinity of the Medina seamounts at the southern IAP boundary, the crust thickens to about 9 km and seismic velocities decrease to 6.8 km s−1 at the crust–mantle boundary. The seismic velocity distribution and depth of the crust–mantle boundary in the IAP document its oceanic nature and support the interpretation of the IAP as a remnant of the Tethys lithosphere with the Malta Escarpment as a transform margin and a Tethys opening in the NNW–SSE direction.