Journal of large-scale research facilities, 3, A122 (2017) http://dx.doi.org/10.17815/jlsrf-3-165 Published: 27.11.2017 DEPAS (Deutscher Geräte-Pool für amphi- bische Seismologie): German Instrument Pool for Amphibian Seismology Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung GFZ German Research Centre for Geosciences * Instrument Coordinators: - Ocean-bottom seismometer: Mechita Schmidt-Aursch, AWI, Am Alten Hafen 26, D-27568 Bremerhaven, Germany, phone: +49-471-4831-1234, email: Mechita.Schmidt-Aursch@awi.de - Onshore stations: Christian Haberland, GFZ, Telegrafenberg, D-14473 Potsdam, Germany, phone: +49-331-288-1810, email: haber@gfz-potsdam.de Abstract: The German Instrument Pool for Amphibian Seismology (DEPAS) provides the infrastruc- ture for onshore, marine and amphibian seismological experiments. It consists currently of approx. 80 ocean-bottom seismometers (OBS) and 95 onshore seismic stations. Broadband sensors and custom- built data loggers enable a broad range of short- and long-term deployments to study architecture and dynamics of the Earth’s interior. The OBS are operated by the Alfred Wegener Institute Helmholtz Cen- tre for Polar and Marine Research (AWI); the onshore stations are managed by the Helmholtz Centre Portsdam GFZ German Research Centre for Geosciences. The DEPAS instruments are available upon request for researchers a�liated to German universities or German research institutes within national or international projects. Applications for stations are evaluated by an external steering committee. Data will be stored in national archives and made available to the public after a waiting period. 1 Introduction More than 70% of the Earth is covered by oceans and seas hiding submarine structures important for geoscienti�c research, natural hazard investigation and resource evaluation. Passive continental mar- gins inherit information about breakup, drift and collision of continents leading to opening and closing of oceanic gateways and hence changing of the thermohaline circulation. These margins are a major source of organic and mineral deposits; but they also carry risks like instable gas hydrates and sub- *Cite article as: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung et al.. (2017). DEPAS (Deutscher Geräte-Pool für amphibische Seismologie): German Instrument Pool for Amphibian Seismology. Journal of large- scale research facilities, 3, A122. http://dx.doi.org/10.17815/jlsrf-3-165 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-3-165 http://dx.doi.org/10.17815/jlsrf-3-165 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 3, A122 (2017) http://dx.doi.org/10.17815/jlsrf-3-165 marine landslides triggering tsunamis. Mid-ocean ridges, mantle plumes, large transform faults and subduction zones witness the evolution of oceanic crust and related magmatic and hydrothermal pro- cesses in crust and mantle; but they are also the location of hazards like long-lasting volcanism and devastating earthquakes and tsunamis. Seismology o�ers invaluable tools to image these structures and determine their tectonics, either by conducting passive monitoring or by performing active exploration. In both cases, acoustic and elas- tic waves spreading out from natural (earthquakes, ocean waves) or arti�cial sources were recorded by seismic stations. Pure onshore installations are not su�cient to map remote submarine targets, therefore the usage of ocean-bottom seismometers (OBS) is essential. Similar technical parameters for onshore stations and OBS are particularly advantageous for achieving a mixed data set of comparable content and quality. To enable marine and amphibian experiments with homogeneous equipment, the DEPAS instrument pool was established in the year 2005 as a large-scale facility for German seismolo- gists. 2 General information The DEPAS instrument pool contains currently about 80 OBS and 95 onshore stations. All stations are equipped with broadband (60 s / 120 s) seismometers and data loggers with a high dynamic range (24 bit / 32 bit). Emphasis was laid on rugged materials and low power consumption of the standalone instruments, so they can record in the �eld up to 18 months. A maximum water depth range of 6000 m for the standard OBS allows a deployment in most o�shore areas, 12 units are specially designed for experiments in very deep basins and subduction zones, they can operate in water depths up to 7300 m. A compact design and simple mounting procedures of the devices allow users to conduct �eld experi- ments with a large number of units (see Figure 1 and Figure 2). The broadband seismometers and recording endurance enable short-term active source experiments as well as long-term passive measurements. A wide variety of methods can be applied to the seis- mic data: raytracing, full-waveform inversion, local seismicity studies, receiver functions, teleseismic tomography, shear wave splitting, surface wave analysis or ambient noise studies. Main research tar- gets are geology and evolution of crust and mantle; thermal structure and magmatic processes in the lithosphere; active tectonics in the crust; occurrence and magnitude of earthquakes; risk assessment of strong motion events and tsunami early warning systems. The onshore and o�shore stations are physically separated; the management of both parts is carried out in close cooperation. The OBS are hosted in Bremerhaven by the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Re- search (AWI; www.awi.de/depas); the onshore stations are integrated in the Geophysical Instrument Pool Potsdam GIPP (GFZ German Research Centre for Geosciences, 2016; www.gfz-potsdam.de/gipp). Scientists of German academic institutes can apply online for the use of instruments. Foreign academics need a German cooperation partner for their projects. All proposals are evaluated twice per year by an external steering committee and an internal advisory board. DEPAS o�ers a rich service package to the instruments’ users: e.g. preparation of the seismic stations and the auxiliary equipment before the experiment, assistance in cruise planning, contract technician for on-board OBS operation, maintenance of the instruments after recovery, software for data conver- sion. Seismic data gathered with DEPAS stations will be archived in international data repositories. Data will be kept con�dential at least three years after retrieval in order to give the users enough time to publish the results. After this embargo period, data will be made available to the public. 2 http://dx.doi.org/10.17815/jlsrf-3-165 https://www.awi.de/forschung/geowissenschaften/geophysik/methoden-und-werkzeuge/ozeanboden-seismometer/depas.html http://www.gfz-potsdam.de/sektion/geophysikalische-tiefensondierung/infrastruktur/geophysikalischer-geraetepool-potsdam-gipp/ https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-3-165 Journal of large-scale research facilities, 3, A122 (2017) 3 Ocean-bottom seismometers (OBS) 3.1 Data loggers SEND Geolon MCS • A/D converter: Sigma-Delta 24 bit, sampling rates 1-1000 sps, SNR > 130 dB • 4 channels (3 geophone, 1 high-impedance hydrophone) plus 3 auxiliary channels • Engineering signals: temperature, humidity, battery voltage • Clock: MCXO, accuracy < 2 ppm, GPS synchronization, external antenna at break-out box • Data: continuous internal format, stored on internal mass storage 20 GB or 32 GB, convertible to MSEED, SAC, GSE, WAV, SEGY • Interfaces: RS232 (communication), IEEE1934 (data download) • Power consumption: approx. 0.5 W @ 500 sps • Weight: 1 kg • Operating temperatures: from -10 °C to +75 °C K.U.M. 6D6 • A/D converter: Sigma-Delta 32 bit @ 250 sps, sampling rates 50-4000 sps, SNR > 142 dB • 4 channels (3 geophone, 1 high-impedance hydrophone), upgrade to more channels possible • Engineering signals: temperature, humidity, battery voltage • Clock: MCXO, linearity < 2 ppm, GPS synchronization, external antenna at break-out box • Data: continuous internal format, stored on removable mass storage up to 2 TB, convertible to MSEED and SEGY • Interfaces: IEEE802.3 and IEEE802.11 (communication) • Power consumption: approx. 0.125 W @ 1000 sps • Weight: 0.24 kg • Operating temperatures: from -10°C to +80 °C 3.2 Seismic sensors Güralp CMG-40T OBS • Flat instrument response (ground velocity): from 60 s /120 s to 50 Hz • 3 orthogonal sensors, max output ± 4.2 V (single ended) • Ground motion sensitivity: approx. 2000 Vs/m @ 1 Hz (single ended) • Power consumption: < 0.1 W @ 5 V • Gimbal mounted, levelling up to ± 55° • Titanium pressure housing, max. operating depth: 6000 m / 7300 m • Weight: 12.5 kg / 13.6 kg • Operating temperature: from -5 °C to +50 °C Trillium Compact OBS • Flat instrument response (ground velocity): from 120 s to 50 Hz • 3 symmetric triaxial sensors; max output ± 40 V (di�erential) • Ground motion sensitivity: approx. 750 Vs/m @ 1 Hz (di�erential) • Power consumption: < 0.18 W (normal operation) • Gimbal mounted, levelling up to ± 25°, operational tilt range up to ± 2.5° without re-levelling • Titanium pressure housing, max. operating depth: 6000 m / 7300 m • Weight: 12.5 kg / 13.6 kg • Operating temperature: from -20 °C to +60 °C 3 http://dx.doi.org/10.17815/jlsrf-3-165 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 3, A122 (2017) http://dx.doi.org/10.17815/jlsrf-3-165 3.3 Hydrophones HighTecInc HTI-01-PCA/ULF and HTI-04-PCA/ULF • Operating frequency: from 100 s to 8 kHz • Sensitivity: approx. -194 dB re: 1V/µ Pa (HTI-01) / -195 dB re: 1V/µ Pa (HTI-04) • Capacitance @ 1 kHz: approx. 47 nF (HTI-01) / 57 nF (HTI-04) • Max. operating depth: 7300 m • Weight: 1.1 kg • Operating temperature from: -3 °C to +150 °C 3.4 Instrument carriers K.U.M. Lobster • Frame and pressure tubes: titanium alloy • Floatation: syntactic foam • Acoustic release transponder: KumQuat K/MT 562 • VHF radio beacon: Novatec RF-700A1 or Metocean Novatec MMB-7500 • Xenon �ashlight: Novatec ST-400A or Metocean Novatec MMF-7500 • Max. operating depth: 6000 m / 7300 m • Weight in air: approx. 340 kg / 320 kg • Operating temperature: from -5 °C to +40 °C K.U.M. Nammu • Frame and pressure tubes: titanium alloy • Floatation: syntactic foam • Acoustic release transponder: KumQuat K/MT 562 • VHF radio beacon: Xeos XMB-11K or Metocean Novatec MMB-7500 • Xenon �ashlight: Xeos XMF-11K or Metocean Novatec MMF-7500 • Max. operating depth: 6000 m • Weight in air: approx. 156 kg • Operating temperature: from -5 °C to +40 °C 3.5 Auxiliary equipment • K.U.M. K/MT 8011M on-board unit for communication with the acoustic release transponders • Seimac DR500 or Communications-Specialists R1000 bearing receiver for localisation of the VHF radio beacons • SEND (GPR12 and GPD30) or K.U.M. (Uhura and Dirc) GPS systems and breakout boxes for com- munication with the data loggers 4 http://dx.doi.org/10.17815/jlsrf-3-165 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-3-165 Journal of large-scale research facilities, 3, A122 (2017) Figure 1: Deployment of a DEPAS ocean-bottom seismometer. Main components are annotated. Inset: OBS after emerging at the sea surface. 4 Onshore stations 4.1 Data loggers (currently 95 units) Earth Data PR6-24 Digital Field Recorder • A/D converter: Sigma-Delta 24 bit, sampling rates 1-3000 sps, SNR 140 dB @ 100 sps to 96 dB @ 3000 sps • 3 or 6 channels plus 4 auxiliary channels • Clock: TCXO, accuracy < 1*10e-6, GPS synchronization, external antenna, continuous or cycled • Data: MSEED format or ASCII, continuous or time window, stored on exchangeable mass storage 10-40 GB • Interfaces: USB, Ethernet, RS232 • Power consumption: from < 1.8 W (GPS cycled) to 2 W (GPS continuous) @ 3*100 sps • Rugged weather-sealed housing • Weight: 3.75-4.3 kg • Operating temperature: from -20 °C to +65 °C 4.2 Seismic sensors (currently 70 units) Güralp CMG-3ESP Compact • Flat instrument response (ground velocity): from 60 s to 50 Hz • 3 orthogonal sensors, max output ±20 V (di�erential) • Generator constant: 2 x 1000 Vs/m (di�erential) • Power consumption: 0.75 W @ 12V • Waterproof housing • Weight: 8.3 kg • Operating temperature: from -10 °C to +65 °C 5 http://dx.doi.org/10.17815/jlsrf-3-165 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 3, A122 (2017) http://dx.doi.org/10.17815/jlsrf-3-165 4.3 Auxiliary equipment • Transport boxes • Cables (sensor, battery, GPS, monitor, etc.) • Limited number of solar panels and solar chargers Figure 2: DEPAS onshore station assembled in the lab without outdoor casing and power supply. Main components are annotated. Acknowledgements The DEPAS instrument pool was initially funded by "Geotechnologien", a geoscienti�c research and development programme raised by the Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG). Additional instruments were �nanced by the Helmholtz Associ- ation of National Research Centres (HGF) and by GFZ and AWI. Sta� is funded by GFZ and AWI. References GFZ German Research Centre for Geosciences. (2016). GIPP: Geophysical Instrument Pool Potsdam. Journal of large-scale research facilities, 2, A64. http://dx.doi.org/10.17815/jlsrf-2-128 6 http://dx.doi.org/10.17815/jlsrf-3-165 http://dx.doi.org/10.17815/jlsrf-2-128 https://creativecommons.org/licenses/by/4.0/ Introduction General information Ocean-bottom seismometers (OBS) Data loggers Seismic sensors Hydrophones Instrument carriers Auxiliary equipment Onshore stations Data loggers (currently 95 units) Seismic sensors (currently 70 units) Auxiliary equipment