Spectra of ocean-bottom seismic noise in the 0.01-10 Hz range

Dozorov, Thomas A.; Soloviev, S. L.

doi:10.1111/j.1365-246x.1991.tb04605.x

Cited by 12 publications

(8 citation statements)

References 27 publications

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“…Their results are comparable to or quieter than other results below 10 Hz (Dozorov and Soloviev, 1991). The OBDS noise level is lower than OBSS above 0.1 Hz.…”

Section: Noise Levelssupporting

confidence: 66%

“…Among the few ocean bottom long-period seismic observations (Sutton et al, 1988;Trevorrow et al, 1990;Dozorov and Soloviev, 1991), we compare with the results obtained from the Columbia-Point Arena Ocean Bottom Seismic Station (OBSS) in Figure 17 (Sutton et al, 1988). Their results are comparable to or quieter than other results below 10 Hz (Dozorov and Soloviev, 1991).…”

Section: Noise Levelsmentioning

confidence: 99%

See 1 more Smart Citation

Performance of the Ocean Broadband Downhole Seismometer at Site 794

Kanazawa¹,

Suyehiro²,

Hirata³

et al. 1992

Proceedings of the Ocean Drilling Program

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The ocean broadband downhole seismometer (OBDS) was successfully emplaced in Hole 794D in the Japan Sea during ODP Leg 128, and OBDS data were obtained continuously aboard JOIDES Resolution during a 60-hr period of real-time observation. During the real-time observation, air-gun profiling was done around Hole 794D using nine ocean-bottom seismometers (OBSs). The OBDS successfully observed air-gun signals from the seismic profiles, five local earthquakes, and an earthquake in Burma (m b 5.4).Signal-to-noise ratios of air-gun signals and local earthquakes observed by the OBDS are higher by over 20 dB than those observed by OBS. The epicentral distance of Burma earthquake was 38.99° to the OBDS. The OBDS could record P, S, and some surface waves from this teleseismic event with good signal-to-noise ratio for both the vertical and horizontal components. Broadband seismic noise spectra (5 m-30 Hz) in the ocean region were revealed for the first time by the OBDS observation. The noise level falls between the two levels of noisy and quiet conditions on land above 10 s. The noise level increases toward longer period. Signals from earthquakes larger than m s = 6 at 30° distance would rise above noise at an 100-s period.Following the real-time observation, an OBDS seafloor recorder was installed and operated for 30 days in event detection mode and time window mode. There was no triggered event. Very long-period data of 1-hr sampling showed only gradual variations without abrupt steplike changes. This indicates that the clamping we used for the OBDS sensors in the hole was sufficiently stable for such a long-term broadband observation.The results obtained in this paper strongly suggest that a broadband downhole seismometer performs well and is dispensable for constructing broadband digital seismograph networks on the ocean floor.

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“…Their results are comparable to or quieter than other results below 10 Hz (Dozorov and Soloviev, 1991). The OBDS noise level is lower than OBSS above 0.1 Hz.…”

Section: Noise Levelssupporting

confidence: 66%

Section: Noise Levelsmentioning

confidence: 99%

Performance of the Ocean Broadband Downhole Seismometer at Site 794

Kanazawa¹,

Suyehiro²,

Hirata³

et al. 1992

Proceedings of the Ocean Drilling Program

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show abstract

“…Although broadband seismic and pressure measurements had been made on the seafloor [ Auld et al , 1969; Barstow et al , 1989; Dozorov and Soloviev , 1992; Latham and Sutton , 1966; Sutton and Barstow , 1990; Webb and Schultz , 1992; Webb , 1988; Webb et al , 1994], the issue of what could be gained by placing a sensor below the seafloor was unresolved prior to the OSNPE. It is convenient in our discussion to define “broadband” as frequencies between 0.001 Hz and 100 Hz; ULF (Ultra Low Frequency) as the band from 0.001 to 1Hz; and VLF (Very Low Frequency) as the band from 1 to 100 Hz.…”

Section: Introductionmentioning

confidence: 99%

Ocean Seismic Network Pilot Experiment

Stephen

Spiess

Collins

et al. 2003

Geochem Geophys Geosyst

103

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[1] The primary goal of the Ocean Seismic Network Pilot Experiment (OSNPE) was to learn how to make high quality broadband seismic measurements on the ocean bottom in preparation for a permanent ocean seismic network. The experiment also had implications for the development of a capability for temporary (e.g., 1 year duration) seismic experiments on the ocean floor. Equipment for installing, operating and monitoring borehole observatories in the deep sea was also tested including a lead-in package, a logging probe, a wire line packer and a control vehicle. The control vehicle was used in three modes during the experiment: for observation of seafloor features and equipment, for equipment launch and recovery, and for power supply and telemetry between ocean bottom units and the ship. The OSNPE which was completed in June 1998 acquired almost four months of continuous data and it demonstrated clearly that a combination of shallow buried and borehole broadband sensors could provide comparable quality data to broadband seismic installations on islands and continents. Burial in soft mud appears to be adequate at frequencies below the microseism peak. Although the borehole sensor was subject to installation noise at low frequencies (0.6 to 50 mHz), analysis of the OSNPE data provides new insights into our understanding of ocean bottom ambient noise. The OSNPE results clearly demonstrate the importance of sediment borne shear modes in ocean bottom ambient noise behavior. Ambient noise drops significantly at high frequencies for a sensor placed just at the sediment basalt interface. At frequencies above the microseism peak, there are two reasons that ocean bottom stations have been generally regarded as noisier than island or land stations: ocean bottom stations are closer to the noise source (the surface gravity waves) and most ocean bottom stations to date have been installed on low rigidity sediments where they are subject to the effects of shear wave resonances. When sensors are placed in boreholes in basement the performance of ocean bottom seismic stations approaches that of continental and island stations. A broadband borehole seismic station should be included in any real-time ocean bottom observatory.

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“…Similarly, the high noise floor on the BBOBS above 1 Hz, relative to HKT, suggests that the two time series will be incoherent. This clearly is cause for concern, particularly for applications on land and for recording local earthquakes, but the low-noise "notch" that characterizes broadband noise spectra in the oceans (Dozorov and Soloviev, 1991;Webb, 1998) and the frequency content of teleseismic and regional earthquake signals make the PMD 2123 well suited for marine use. It would be helpful to compare signals for a local event or explosion that contains coherent energy above 1 Hz, but the Hockley region is relatively aseismic and we did not record a local event.…”

Section: Introductionmentioning

confidence: 98%

“…This combination is referred in this paper as BBOBS. See text for details about the UTIG OBS package. The STS-1, digitized by a 24-bit Quanterra Q680 and recorded by IRIS's GSN, is referred to here as HKT. among the Japanese (e.g., Suyehiro, 1997), French (Montagner et al, 1994), and Russians (Dozorov and Soloviev, 1991) internationally. More recently, a large and diverse group of investigators collaborated to collect earthquake data with OBSs at the Southern East Pacific Rise for the mantle electromagnetic and tomography (MELT) experiment (Forsyth et al, 1998a).…”

Section: Introductionmentioning

confidence: 99%

Field Test of an Inexpensive, Small Broadband Ocean-Bottom Seismograph

Pulliam¹

2003

Bulletin of the Seismological Society of America

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We conducted tests of a three-component broadband ocean-bottom seismograph (OBS), including side-by-side comparisons with the broadband Global Seismic Network/U.S. National Seismic Network station HKT at Hockley, Texas, and a 28-day deployment in the Gulf of Mexico. Our goals were to evaluate seismometer performance and determine whether our seafloor deployment strategy allows useful earthquake data to be collected. The seismometer generally performed well, but showed unexpectedly high intrinsic noise at frequencies above 1 Hz and produced occasional spikes that were confined to a single component at a given time. We identified 32 earthquakes from the Gulf of Mexico data; only five additional events were observed at the nearby, highly sensitive station HKT on land. While noise levels were higher throughout the 0.01-20 Hz frequency band in the Gulf of Mexico compared with HKT, site amplification effects in the gulf were only significant at frequencies above 1 Hz and power in most earthquake signals peaked at frequencies below 0.1 Hz, nearly coinciding with a minimum in background noise. We found the seismometer and OBS package encouraging for far-regional and teleseismic studies, given the low cost of the OBS and inexpensive means for deployment and recovery, but less encouraging for detecting and locating small-magnitude local and near-regional events.

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Spectra of ocean-bottom seismic noise in the 0.01-10 Hz range

Cited by 12 publications

References 27 publications

Performance of the Ocean Broadband Downhole Seismometer at Site 794

Performance of the Ocean Broadband Downhole Seismometer at Site 794

Ocean Seismic Network Pilot Experiment

Field Test of an Inexpensive, Small Broadband Ocean-Bottom Seismograph

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