Ingo Klaucke

RV SONNE Fahrtbericht / Cruise Report SO226 - CHRIMP CHatham RIse Methane Pockmarks, 07.01. - 06.02.2013 / Auckland – Lyttelton, 07.02. – 01.03.2013 / Lyttelton - Wellington

[Davy et al., 2010a] reported on pockmark observations along the Chatham Rise, offshore New Zealand’s South Island. The observed structures fall into three categories: features of approx. 150 m diameter are found in water depths of 500 m – 700 m, depressions with diameters of up to 5 km and the largest structures with diameters of up to 11 km were observed in water depth of 800 - 1100 m. Seismic sections across the pockmarks were available at only a few locations and mainly consisted of Parasound data. Multiple layers of small pockmarks could be correlated with sediment interfaces of increased amplitudes that correspond to the transitions between glacial maxima and minima. Consequently [Davy et al., 2010a] assumed that sealevel lowstands during glacial maxima caused the dissolution of gas hydrates and hence triggered the formation of pockmarks. Project SO226 CHRIMP aimed to test this hypothesis with an extended data base. Additional bathymetric coverage revealed multiple occurrences of large and medium size structures. Three working areas were selected along the Chatham Rise each representing one of the three types / sizes of seafloor depression. nArea one was chosen to be centred around 178°40’E with the largest pockmark structure of up to 15 km diameter. From the extended bathymetric coverage a south-west to north-east oriented alignment of three similar structures was observed. Seismic sections show a highly variable sedimentation. Inside the structures all sediments had been fully eroded to a surface that can be mapped throughout the entire region. All observed pockmarks show a radial eroded rim to the South-West with a base that corresponds to the above mentioned erosional surface. Near vertical faults and nblanking patterns are found underneath the eroded rim of the structures. Shallow bright spots with negative polarity are interpreted as indicators for free gas. Nevertheless no signs were found for active fluid venting above the structure or in the surrounding. nThe second area centred around 177°05’E hosts medium-size pockmarks. Five depressions were nmapped, but some of them might be formed by overlapping pockmarks. Partly resedimented the nstructures show an eroded southern part with a sharp radial rim. Indifferent from area one a roughly 250 m wide blanking zone was found underneath one of the pockmarks. The area is imaged right above a conical shaped upward extension of a deeper sediment interface. From the 3D data the interface shows a rough topography. The conical structure and the blanking area are interpreted as an ancient feeder channel. This chimney terminates at an erosional interface, which forms the base of the seafloor depression. Multiple events of erosion, sedimentation and slumping have been identified above the erosional surface. Again water column imaging and geochemical analyses do not show indications for active methane venting within this area. nThe third working area was chosen to be centred 174°35’E where a large zone of small pockmarks nwas known from earlier mapping. A 2D seismic profile confirms the existence of stacked pockmark layers. The wide funnel shaped opening of the buried pockmarks terminates at distinguished sediment interfaces that show an increased reflection amplitude. This corresponds to the interpretation of [Davy et al., 2010a]. At greater depth the horizontal layering of the sediments is not interrupted. nAs with the previous two working areas there is no sign of a BSR and active methane venting could not be confirmed by water column imaging or geochemical analyses. nIn summary all three areas do show images of gas migration pathways of various sizes within the deeper sediments. Nevertheless active venting of fluids could not be confirmed. Therefore other models need to be developed to explain todays still sharp defined rims of the pockmark-like seafloor depressions.

Echolot - Die Tiefe hören, 4.000 Jahre Tiefenmessung im Ozean: die Entwicklung des Echolots und seine Bedeutung für das Verständnis des Systems Erde

Diese Broschure und die gleichnamige Ausstellung befassen sich mit der Entwicklung des Echolots, nfur das der Kieler Physiker und Unternehmer Alexander Behm im Jahr 1913 das erste Patent erhielt. nErfahren Sie mehr uber die Geschichte der Tiefenmessung im Ozean – von den ersten Handloten nim alten Agypten uber die dampfgetriebenen Lotmaschinen des 19. Jahrhunderts, der Entwicklung der ozeanischen Tiefenkarten bis hin zur heutigen Vermessung des Meeresbodens mit modernen Facherecholoten.

RV SONNE 252 Cruise Report / Fahrtbericht,Yokohama: 05.11.2016 - Nouméa: 18.12.2016.SO252: RITTER ISLAND Tsunami potential of volcanic flank collapses

Large volcanic debris flows associated with volcanic island flank collapses may cause devastating tsunamis as they enter the ocean. Computer simulations show that the largest of these volcanic debris flows on oceanic islands such as Hawaii or the Canaries can cause ocean-wide tsunamis (Lovholt et al., 2008; Waythomas et al., 2009). However, the magnitude of these tsunamis is subject to on-going debate as it depends particularly on landslide transport and emplacement processes (Harbitz et al. 2013). A robust understanding of these factors is thus essential in order to assess the hazard of volcanic flank collapses. Recent studies have shown that emplacement processes are far more complex than assumed previously. With a collapsed volume of about 5 km3 the 1888 Ritter Island flank collapse is the largest in historic times and represents an ideal natural laboratory for several reasons: (I) The collapse is comparatively young and the marine deposits are clearly visible, (II) the pre-collapse shape of the island is historically documented and (III) eyewitness reports documenting tsunami arrival times, run-up heights and inundation levels on neighboring islands are available. We propose to collect bathymetric, high resolution 2D and 3D seismic data as well as seafloor samples from the submarine deposits off Ritter Island to learn about the mobility and emplacement dynamics of the 1888 flank collapse landslide. A comparison to similar studies from other volcanic islands will provide an improved understanding of emplacement processes of volcanic island landslides and their overall tsunamigenic potential. In addition, a detailed knowledge of the 1888 landslide processes in combination with tsunami constraints from eyewitness reports provides a unique possibility to determine the landslide velocity, which can then be used in subsequent hazard analyses for ocean islands.

Fahrtbericht / Cruise Report SO244/1 - GeoSEA: Geodetic Earthquake Observatory on the Seafloor, Antofagasta (Chile) - Antofagasta (Chile), 30.10.2015 - 24.11.2015

The majority of M>8.5 active plate boundary earthquakes has hypocenters located beneath the noceans in subduction zones. Post-hoc analysis shows that most of the surface deformation nrelated to co-seismic stress release takes place on the seafloor, in many cases unleashing major ntsunamis. The structure and morphology of the seafloor and shallow subbottom thus stores ncrucial information on sub-seafloor processes, such as permanent deformation by seismic slip or naseismic creep within the overriding plate and earthquake and tsunami generation. n nWe have mapped the seafloor seaward of the Northern Chilean coast between about 19°S and n22°S down to the Northern Chile deep sea trench, using the ship-based Multibeam Echosounder nEM122, Parasound, and AUV (autonomous underwater vehicle) – in selected subareas - at nsufficient resolution to identify active tectonic fault structures and submarine mass wasting nstructures, to quantitatively assess young and active deformation of the overriding plate in the narea, and quantify the extent of recent catastrophic downslope mass movements of sediment. nFurthermore, the investigations serve as a site survey for the deployment of the GeoSEA nseafloor geodetic array, to be installed immediately after completion of this cruise. n nThe investigations were made timely by the 1st April 2014 Pisagua M=8.2 earthquake, that nruptured the plate interface in the northern part of the area of investigation. The central and nsouthern parts are located in the last remaining locked seimotectonic segment along the Chilean nactive margin. In addition to providing the first data base for geomorphological and tectonic ninterpretation of geo-processes at the seafloor, the bathymetric mapping done during SO244 nLeg 1 will provide an important data reference for possible post-earthquake surveys once this nseismotectonic segment will have broken in the future.

FS MARIA S. MERIAN Fahrtbericht / Cruise ReportMSM34/1 & 2 - SUGAR Site ; Varna – Varna,06.12.13 – 16.01.14

During the two legs of cruise MSM34 of R/V MARIA S. MERIAN regional 2D seismic nsurveying, high resolution 2D and 3D seismic imaging, geo-chemical sampling, heatflow nmeasurements and long-term piezometer installations were undertaken. nA grid of 28 2D seismic profiles was collected across the palaeo Danube delta. A number nof inactive and partly buried channel systems could be mapped. Most of them were underlain nby one or more bottom simulation reflectors (BSR). Based on the seismic brute stack images nand the limits of the MeBo drilling device a prospective channel system with indications for npossible gas hydrate formation at shallow depth (BSR, inverted strong amplitudes) could be nidentified in about 1500 m water depth. High resolution 2D seismic and 3D P-Cable seismic nwere used together with OBS deployments in order to allow structural mapping and physical ndescription of the channel infill. Heatflow measurements and geochemical analyses of gravity nand multi corer samples accompany these investigations. Neither the multibeam water column nimages nor Parasound records show any evidence of flares (gas bubbles in the water column) nin this working area suggesting a well sealed hydrate reservoir. nActive gas expulsion from the seafloor was observed at about 200 m water depth circling naround a slump area. The base plane of the failed sediment volume builds the current seafloor nat about 600 m to 700 m water depth. On regional 2D seismic profiles a BSR has been nmapped underneath the slope failure with unexpectedly strong upward bending. High nresolution 2D and 3D P-Cable seismic investigations with complementary OBS deployment nwill allow imaging the BSR outline. Moreover velocity analyses, heatflow measurements and ngeo-chemical samples will be available for a detailed description of hydrate distribution and nsediment parameters. nIn a third working area high resolution 2D seismic reflection profiles were acquired across na fully buried channel system. Together with the regional seismic lines slope failure of the nchannel fill material can be studied across the slope extension of the system.