Measuring of clock drift rates and static time offsets of ocean bottom stations by means of ambient noise

Hannemann, Katrin; Krüger, Frank; Dahm, Torsten

doi:10.1093/gji/ggt434

Cited by 49 publications

(34 citation statements)

References 10 publications

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“…Assuming that the skew accumulated linearly over the deployment period, the clock error can be corrected for any moment in time. Previous studies (Hannemann et al, 2014;Scholz, 2014) show that linearity is a good first order approximation for the clocks used in the DEPAS instruments. For the LCPO2000 instruments used in the INSU pool, Gouedard et al (2014) found that drift rates can vary over the course of days.…”

Section: Estimation Of Clock Errormentioning

confidence: 91%

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Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean

et al. 2016

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Abstract. RHUM-RUM is a German-French seismological experiment based on the sea floor surrounding the island of La Réunion, western Indian Ocean (Barruol and Sigloch, 2013). Its primary objective is to clarify the presence or absence of a mantle plume beneath the Reunion volcanic hotspot. RHUM-RUM's central component is a 13-month deployment (October 2012 to November 2013) of 57 broadband ocean bottom seismometers (OBS) and hydrophones over an area of 2000 × 2000 km 2 surrounding the hotspot. The array contained 48 wideband OBS from the German DE-PAS 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.This article 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.The INSU seismic sensors stand away from their OBS frames, whereas the DEPAS sensors are integrated into their frames. 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, but in addition the DEPAS intruments are affected by significant selfnoise at long periods, including on the vertical channels. By comparison, the INSU instruments are much quieter at periods > 30 s and hence better suited for long-period signals 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. Additionally, the wideband sensor has only half the power consumption of the broadband INSU seismometers.

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Section: Estimation Of Clock Errormentioning

confidence: 91%

“…Using cross-correlation of ambient noise, SensSchönfelder (2008) presented a method to determine the relative clock error between two seismometers a posteriori, which Hannemann et al (2014) successfully applied to OBS data. Likewise, Scholz (2014) Figure 7.…”

Section: Estimation Of Clock Errormentioning

confidence: 99%

Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean

et al. 2016

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“…One of the twelve stations had two clamped components (filled red triangle in Fig. 8, Hannemann et al 2014), therefore we do not use the data from this station for our analysis. The data are time corrected (Hannemann et al 2014) and the horizontal components are oriented by using P phases and Rayleigh phases (Stachnik et al 2012;Sumy et al 2015) of know teleseismic events.…”

Section: Datamentioning

confidence: 99%

Oceanic lithosphericS-wave velocities from the analysis ofP-wave polarization at the ocean floor

Hannemann¹,

Dahm

Lange³

2016

Geophys. J. Int.

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S U M M A R YOur knowledge of the absolute S-wave velocities of the oceanic lithosphere is mainly based on global surface wave tomography, local active seismic or compliance measurements using oceanic infragravity waves. The results of tomography give a rather smooth picture of the actual S-wave velocity structure and local measurements have limitations regarding the range of elastic parameters or the geometry of the measurement. Here, we use the P-wave polarization (apparent P-wave incidence angle) of teleseismic events to investigate the S-wave velocity structure of the oceanic crust and the upper tens of kilometres of the mantle beneath single stations. In this study, we present an up to our knowledge new relation of the apparent Pwave incidence angle at the ocean bottom dependent on the half-space S-wave velocity. We analyse the angle in different period ranges at ocean bottom stations (OBSs) to derive apparent S-wave velocity profiles. These profiles are dependent on the S-wave velocity as well as on the thickness of the layers in the subsurface. Consequently, their interpretation results in a set of equally valid models. We analyse the apparent P-wave incidence angles of an OBS data set which was collected in the Eastern Mid Atlantic. We are able to determine reasonable S-wave-velocity-depth models by a three-step quantitative modelling after a manual data quality control, although layer resonance sometimes influences the estimated apparent S-wave velocities. The apparent S-wave velocity profiles are well explained by an oceanic PREM model in which the upper part is replaced by four layers consisting of a water column, a sediment, a crust and a layer representing the uppermost mantle. The obtained sediment has a thickness between 0.3 and 0.9 km with S-wave velocities between 0.7 and 1.4 km s −1 . The estimated total crustal thickness varies between 4 and 10 km with S-wave velocities between 3.5 and 4.3 km s −1 . We find a slight increase of the total crustal thickness from ∼5 to ∼8 km towards the South in the direction of a major plate boundary, the Gloria Fault. The observed crustal thickening can be related with the known dominant compression in the vicinity of the fault. Furthermore, the resulting mantle S-wave velocities decrease from values around 5.5 to 4.5 km s −1 towards the fault. This decrease is probably caused by serpentinization and indicates that the oceanic transform fault affects a broad region in the uppermost mantle. Conclusively, the presented method is useful for the estimation of the local S-wave velocity structure beneath ocean bottom seismic stations. It is easy to implement and consists of two main steps: (1) measurement of apparent P-wave incidence angles in different period ranges for real and synthetic data, and (2) comparison of the determined apparent S-wave velocities for real and synthetic data to estimate S-wave velocity-depth models.Key words: Time-series analysis; Body waves; Theoretical seismology; Oceanic transform and fracture zone processes. I N T RO D U C T I O NThe p...

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“…At station 12, the drift correction was not possible due to the cessation of recording during the observation period. We therefore estimated the clock delays at these two stations from the temporal changes of CCFs as done by Sens-Schönfelder (2008) for land seismic records without GPS reception and recently by Hannemann et al (2013) and Gouedard et al (2014) for oceanic regions. Fig.…”

Section: Correction For Clock Delays and Instrumental Responsesmentioning

confidence: 99%

Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records

Takeo¹,

Forsyth

Weeraratne

et al. 2014

Geophysical Journal International

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S U M M A R YWe analysed background surface waves in seismic ambient noise by cross-correlating continuous records of eight ocean bottom seismometers and nine differential pressure gauges deployed in the northwestern Pacific Ocean by the PLATE project. After estimating the clock delay and instrumental phase responses of differential pressure gauges by using cross-correlation functions, we measured average phase velocities in the area of the array for the fundamental-, first higher-and second higher-mode Rayleigh waves, and the fundamental-mode Love waves at a period range of 3-40 s by waveform fitting. We then measured phase-velocity anomalies of fundamental-mode and first higher-mode Rayleigh waves for each pair of stations at a period range of 5-25 s, and corrected the effect of variation in water-depths. The seismic anomalies imply the presence of strong azimuthal anisotropy beneath the eastern part of array. The direction of maximum velocity is approximately N35• E in the fossil seafloor spreading direction perpendicular to magnetic lineations from the ancient triple junction at this location. The peak-to-peak intensity of shear-wave velocity anisotropy in the mantle is ∼7 per cent.

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Measuring of clock drift rates and static time offsets of ocean bottom stations by means of ambient noise

Cited by 49 publications

References 10 publications

Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean

Performance report of the RHUM-RUM ocean bottom seismometer network around La Réunion, western Indian Ocean

Oceanic lithosphericS-wave velocities from the analysis ofP-wave polarization at the ocean floor

Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records

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