Geophysical investigations in the emerged and submerged Atlantic Coastal Plain: PART III: BARNEGAT BAY, NEW JERSEY, SECTION

Ewing, Maurice; Woollard, George P.; Vine, Allyn C.

doi:10.1130/gsab-50-257

Cited by 73 publications

(16 citation statements)

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“…While these integral inversions were formed under the assumption of a smoothly varying V(Z) function, discrete methods were developed to accommodate traveltime data arising from shallower, layered structures. These consisted of solutions for equation (5), and in the case of dipping layers, equations (9a) and (9b) (Slotnick, 1936;Ewing et al, 1939;Mota, 1954;Adachi, 1954). Below, we show how these discrete methods can be applied to T -p mapped CMP data without the necessity of distinguishing between refracted and reflected arrivals, and in the presence of dip.…”

Section: Was Solved By Herglotz (1907) Batemann (1907) and Weichertmentioning

confidence: 99%

The traveltime equation, tau‐p mapping, and inversion of common midpoint data

1981

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Seismic traveltime data can be described in terms of instantaneous slope (dT/dX) and intercept time (7). With this parameterization, the most general form of the traveltime equation is developed and found to be valid for reflections and refractions, all source-receiver offsets, and all commonly used experimental geometries. For common sourcereceiver experiments, the instantaneous slope of the traveltime data represents the true horizontal ray parameter p, and the intercept time is the sum along the ray of thicknessvertical slowness products referenced to the fixed surface station. For common midpoint (CMP) experiments, we show that the instantaneous slope is the average slowness of upgoing and downgoing rays at the surface, and the intercept time is again the sum of thickness-vertical slowness products, but referenced to the common midpoint. This inherent averaging immediately explains the superiority of the CMP experiment in the presence of dip. In addition to providing a general traveltime equation, we find that 7-p parameterization reorganizes traveltime data in a way which greatly facilitates interpretation. For reflections, the 7-p trajectories are sums of ellipses and all turning rays (whether refracted or postcritically reflected) combine to form a well defined and easily identified trajectory. We present a method for deriving a velocity-depth function from this trajectory which is applicable to both refracted and reflected arrivals.

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Section: Was Solved By Herglotz (1907) Batemann (1907) and Weichertmentioning

confidence: 99%

The traveltime equation, tau‐p mapping, and inversion of common midpoint data

1981

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“…Such layers can result from tau-sum inversion in two situation-ne occurs if a pre-critical reflection is included in the inversion, and the other if a low-velocity zone is present in the real Earth structure. Considering the first of these we note that the tau-sum method derives layer thicknesses in an Earth approximated by a stack of uniform-velocity layers by a method that is essentially an extension of the classic slope-intercept method of Ewing, Woollard & Vine (1939), who used head-wave data. showed that it could be generalized to include diving waves and post-critical reflections.…”

Section: P-wave Velocity (5) Structurementioning

confidence: 99%

A Low-Velocity Zone Within the Layer 3 Region of 118 Myr Old Oceanic Crust In the Western North Atlantic

Mithal

Mutter

1989

Geophysical Journal International

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S U M M A R Y During the North Atlantic transect (NAT) experiment 11 expanding spread profiles (ESPs) were acquired using a 3300 cubic inch, 30-element tuned airgun array (S/V Prospekta) and a &-channel seismic streamer (R/V Moore). Extremely high-density seismograms were obtained that have allowed us to transform the observed data to the domain of intercept time and ray parameter (tau-p) with high precision. Velocity structures have been obtained by tau-sum inversion, ray tracing, and synthetic WKBJ and reflectivity seismogram methods both in tau-p and x-t domains.A detailed analysis of ESP 5 suggests the presence of a low-velocity zone within the lower oceanic crust at the location of magnetic anomaly MO (118 Ma). It is apparently 2.86 km thick, has a P-wave velocity of 6.5 km s-', S-wave velocity of 3.6 km s-', and occupies much of the depth interval normally associated with oceanic layer 3. Converted shear wave arrivals have been used to obtain the shear velocity structure. We find that the Vp/Vs ratio in the uppermost part of the crust is about 1.9, and much of the crustal section has a VJV, ratio greater than ~. Attenuation of P-and S-waves has been studied by amplitude analysis, and we find that in most of the lower crust Q, is equal to Qp. Comparison with solutions from ESPs in younger and older parts of the basin suggests that ESP 5 is unique in displaying a low-velocity zone. Despite this the total thickness at ESP 5 is not significantly different than at other locations. We suggest that this provides strong evidence that the low-velocity zone occurs within the lower crust, and does not result from serpentinization of the upper mantle beneath thin oceanic crust.

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“…Three reports have been published to date, P a rt I by Ewing, C rary, and R utherford (1937), P a rt I I by M iller (1937), and P a rt I I I by Ewing, Woollard, and Vine (1939).…”

Section: "Exact Information In Regard To the Basement Of The Coastal mentioning

confidence: 83%

Status of geological and geophysical investigations on the Atlantic and Gulf Coastal Plain

Leet¹

1940

Geological Society of America Bulletin

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Geophysical investigations in the emerged and submerged Atlantic Coastal Plain: PART III: BARNEGAT BAY, NEW JERSEY, SECTION

Cited by 73 publications

References 0 publications

The traveltime equation, tau‐p mapping, and inversion of common midpoint data

The traveltime equation, tau‐p mapping, and inversion of common midpoint data

A Low-Velocity Zone Within the Layer 3 Region of 118 Myr Old Oceanic Crust In the Western North Atlantic

Status of geological and geophysical investigations on the Atlantic and Gulf Coastal Plain

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