Preliminary interpretation of a marine deep seismic sounding survey in the region of Explorer ridge

1976 ◽  
Vol 13 (11) ◽  
pp. 1545-1555 ◽  
Author(s):  
R. M. Clowes ◽  
S. J. Malecek
Keyword(s):  
Upper Mantle ◽  
Vertical Component ◽  
Thick Layer ◽  
Deep Seismic Sounding ◽  
Ocean Bottom ◽  
Reflected Waves ◽  
Juan De Fuca Plate ◽  
Seismic Sounding ◽  
First Arrival ◽  
Marine Seismic

A marine seismic system for recording near-vertical incidence to wide-angle reflected waves and refracted waves with penetration from the ocean bottom to the upper mantle (deep seismic sounding or DSS) has been developed. Signals from six individual hydrophones suspended at 45 m depth from a 600 m cable trailed behind the receiving ship are recorded in digital form. Using charges ranging from 2.3 to 280 kg, two reversed DSS profiles were recorded in the region of Explorer ridge during 1974. A preliminary interpretation of the profiles based on first-arrival information in the range 4 to 80 km has been made.The reversed profile run across the ridge showed no anomalous effects as the ridge was crossed; the profile on Juan de Fuca plate, paralleling the ridge, exhibited traveltime branch offsets and delays. These have been interpreted as due to faulting with a vertical component of offset of about 4 km. The reversed upper mantle velocities are 7.85 and'7.30 km/s indirections perpendicular and parallel to the ridge. Anisotropy is proposed to explain these different velocities and gives a 7% anisotropic effect. The data require that 'layer 2' comprise at least two layers with velocities of 4.13 km/s and 5.25 km/s and individual depth extents ranging from 1 to 2 km. Compared with crustal sections from other ridge areas, the interpretation gives a thick 'layer 3' (up to 6 km) near the ridge crest. The sub-bottom thickness of the oceanic crust varies between 7 and 9 km, except in the faulted region, where the 7.30 km/s material is present less than 3 km from the bottom.

scholarly journals Crustal and upper mantle structure in the Ryukyu Island Arc deduced from deep seismic sounding

1990 ◽  
Vol 102 (3) ◽  
pp. 631-651 ◽  
Author(s):  
T. Iwasaki ◽  
N. Hirata ◽  
T. Kanazawa ◽  
J. Melles ◽  
K. Suyehiro ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Island Arc ◽  
Deep Seismic Sounding ◽  
Ryukyu Island ◽  
Mantle Structure ◽  
Upper Mantle Structure ◽  
Seismic Sounding

scholarly journals Post-critical SsPmp and its applications to Virtual Deep Seismic Sounding (VDSS) – 2: 1-D imaging of the crust/mantle and joint constraints with receiver functions

2019 ◽  
Vol 219 (2) ◽  
pp. 1334-1347 ◽  
Author(s):  
Tianze Liu ◽  
Simon L Klemperer ◽  
Gabriel Ferragut ◽  
Chunquan Yu
Keyword(s):  
Upper Mantle ◽  
Receiver Functions ◽  
Deep Seismic Sounding ◽  
Moho Depth ◽  
Joint Analysis ◽  
Crust And Upper Mantle ◽  
Slave Craton ◽  
Single Station ◽  
Seismic Sounding ◽  
Novel Method

SUMMARY Virtual Deep Seismic Sounding (VDSS) has emerged as a novel method to image the crust–mantle boundary (CMB) and potentially other lithospheric boundaries. In Part 1, we showed that the arrival time and waveform of post-critical SsPmp, the post-critical reflection phase at the CMB used in VDSS, is sensitive to several different attributes of the crust and upper mantle. Here, we synthesize our methodology of deriving Moho depth, average crustal Vp and uppermost-mantle Vp from single-station observations of post-critical SsPmp under a 1-D assumption. We first verify our method with synthetics and then substantiate it with a case study using the Yellowknife and POLARIS arrays in the Slave Craton, Canada. We show good agreement of crustal and upper-mantle properties derived with VDSS with those given by previous active-source experiments and our own P receiver functions (PRF) in our study area. Finally, we propose a PRF-VDSS joint analysis method to constrain average crustal Vp/Vs ratio and composition. Our PRF-VDSS joint analysis shows that the southwest Slave Craton has an intermediate crustal composition, most consistent with a Mesoarchean age.

Multiple water reflections recorded at the ocean bottom

1978 ◽  
Vol 15 (1) ◽  
pp. 78-85 ◽  
Author(s):  
George A. McMechan
Keyword(s):  
Vertical Component ◽  
Standard Technique ◽  
Ocean Bottom ◽  
Seismic Profiles ◽  
Multiple Reflections ◽  
Air Water Interface ◽  
Time Distance ◽  
Marine Seismic ◽  
Ray Parameter ◽  
Sediment Interface

The use of direct arrivals and multiple reflections that have travelled completely in water from source to receiver to determine epicentral distances is a standard technique in the analysis of marine seismic profiles. The configuration of a source at the air–water interface and a seismometer at the water–sediment interface is investigated in the ray parameter – distance plane and the travel time – distance plane. Vertical component synthetic seismograms are computed by the Cagniard – de Hoop algorithm and are compared with seismograms recorded at the ocean bottom. The results explain the prominent features of the observed wavetrains, including the asymptotic behaviour of arrivals, the location of caustics and the variable observability of arrivals as a fu nction of distance.

Elimination of free‐surface related multiples without need of the source wavelet

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 327-341 ◽  
Author(s):  
Lasse Amundsen
Keyword(s):  
Free Surface ◽  
Vertical Component ◽  
Ocean Bottom ◽  
Pressure Derivative ◽  
Direct Wave ◽  
Marine Source ◽  
Marine Seismic ◽  
Multiple Elimination ◽  
Data Frequency ◽  
Source Array

This paper presents a new, wave‐equation based method for eliminating the effect of the free surface from marine seismic data without destroying primary amplitudes and without any knowledge of the subsurface. Compared with previously published methods which require an estimate of the source wavelet, the present method has the following characteristics: it does not require any information about the marine source array and its signature, it does not rely on removal of the direct wave from the data, and it does not require any explicit deghosting. Moreover, the effect of the source signature is removed from the data in the multiple elimination process by deterministic signature deconvolution, replacing the original source signature radiated from the marine source array with any desired wavelet (within the data frequency‐band) radiated from a monopole point source. The fundamental constraint of the new method is that the vertical derivative of the pressure or the vertical component of the particle velocity is input to the free‐surface demultiple process along with pressure recordings. These additional data are routinely recorded in ocean‐bottom seismic surveys. The method can be applied to conventional towed streamer pressure data recorded in the water column at a depth which is greater than the depth of the source array only when the pressure derivative can be estimated, or even better, is measured. Since the direct wave and its source ghost is part of the free‐ surface demultiple, designature process, the direct arrival must be properly measured for the method to work successfully. In the case when the geology is close to horizontally layering, the free‐surface multiple elimination method greatly simplifies, reducing to a well‐known deterministic deconvolution process which can be applied to common shot gathers (or common receiver gathers or common midpoint gathers when source array variations are negligible) in the τ-p domain or frequency‐wavenumber domain.

A marine deep seismic sounding system

1977 ◽  
Vol 14 (6) ◽  
pp. 1276-1285 ◽  
Author(s):  
Ron M. Clowes
Keyword(s):  
Dynamic Range ◽  
Digital Data ◽  
Ocean Bottom ◽  
Time Code ◽  
Quality Of Data ◽  
Reflected Waves ◽  
Analog Tape ◽  
Marine Seismic ◽  
Record Section ◽  
Seismic System

A marine seismic system for recording near-vertical incidence to wide-angle reflected waves and refracted waves with penetration from the ocean bottom to the upper mantle has been developed. Operations require two ships, one the receiving vessel, the other the shooting ship. Seismic signals are received by six individual hydrophone assemblies suspended at 45-m depth from a neutrally buoyant 610-m cable trailed from the receiving vessel. After filtering and amplification, the seismic data plus the WWVB radio time code are recorded on a multichannel, 14-bit digital data acquisition system. The shooting ship detonates explosive charges as it proceeds along a predetermined course. In order to calculate origin times and to monitor the source signature, the signal from a single hydrophone and the WWVB time code are recorded on a 2-channel chart recorder and 4-channel FM analog tape transport. The digital recording and multiple receivers provide increased dynamic range relative to analog methods, improve the capability for detecting subcritical incidence reflections, and enable the use of data processing techniques, including stacking of weak refraction arrivals. Examples of an expanding reflection record section from a deep water sedimentary basin west of Vancouver Island and of a refraction record section recorded across Explorer Ridge spreading centre show the quality of data which are acquired with the marine seismic system.

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