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| Titel |
Noise on broadband Ocean Bottom Seismometers (OBS) from the German (DEPAS) and French (INSU) instruments pools as recorded in the RHUM-RUM project |
| VerfasserIn |
Simon C. Stähler, Karin Sigloch, Guilhem Barruol, Kasra Hosseini, Wayne C. Crawford, Mechita Schmidt-Aursch, Maria Tsekhmistrenko, John-Robert Scholz, Martha Deen, Alessandro Mazzullo |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124603
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| Publikation (Nr.) |
 EGU/EGU2016-4060.pdf |
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| Zusammenfassung |
| A long-standing discussion in the OBS community is about the influence of OBS design on
noise levels of seismic records. We present results from the RHUM-RUM experiment in the
Indian Ocean.
RHUM-RUM is a German-French seismological experiment based on the sea floor
surrounding the island of La Réunion, western Indian Ocean. RHUM-RUM’s central
component is a 13-month deployment (Oct 2012 to Nov 2013) of 57 broad- and wideband
ocean bottom seismometers (OBS) and hydrophones over an area of 2000x2000 km2
surrounding the hotspot. The array contained 48 wideband OBS from the German DEPAS
pool and 9 broadband OBS from the French INSU pool. It is the largest deployment of
DEPAS and INSU OBS so far, and the first joint experiment. Therefore it allows to compare
the performance of these distinct instrument types in different ocean-floor environments. The
INSU seismic sensors stand away from their OBS frames, whereas the DEPAS sensors are
integrated into theirs.
At long periods (>10 s), the DEPAS seismometers are affected by significantly
stronger noise than the INSU seismometers. On the horizontal components, this can be
explained by tilting of the frame and buoy assemblage, e.g., through the action of
ocean-bottom currents. However, the long period noise level on the vertical components
suggests that the DEPAS intruments are also affected by significant self-noise of the
CMG-40TOBS seismometer itself. By comparison, the INSU instruments (Trillium 240OBS
sensors) are much quieter at periods >30 s and hence better suited for long-period
studies.
The trade-off of the instrument design is that the integrated DEPAS setup is easier to
deploy and recover, especially when large numbers of stations are involved or fast
deployment/recovery of the instruments is desired (e.g. active experiments). Additionally, the
wideband sensor has only half the power consumption of the broadband INSU
seismometers.
This presentation also reviews network performance and data quality: Of the 57 stations,
46 and 53 yielded good seismometer and hydrophone recordings, respectively. The 19,751
total deployment days yielded 18,735 days of hydrophone recordings and 15,941 days of
seismometer recordings, which are 94% and 80% of the theoretically possible yields. |
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