Multiple‐source Werner deconvolution

Geophysics ◽  
1993 ◽  
Vol 58 (12) ◽  
pp. 1792-1800 ◽  
Author(s):  
Richard O. Hansen ◽  
Marc Simmonds
Keyword(s):  
Analytic Signal ◽  
The Body ◽  
Multiple Source ◽  
Juan De Fuca Ridge ◽  
Spreading Center ◽  
Complex Polynomial ◽  
Aeromagnetic Data ◽  
Linear Least Squares ◽  
Linear Least Squares Problem ◽  
Juan De Fuca

A reformulation of the Werner deconvolution algorithm using the analytic signal is extended to multiple source bodies. The extended algorithm involves solving a linear least‐squares problem; the coefficients so obtained determine a complex polynomial whose roots define the locations and depths of the body contacts. The extended algorithm has been used to map the structure of the Cobb offset zone of the Juan de Fuca Ridge from aeromagnetic data; both the top and bottom of the spreading center basalts can be delineated. Connections between the multiple‐source Werner technique and CompuDepth™ are discussed.

Locating N Points of a Rigid Body on N Given Planes

2004 ◽  
Author(s):  
Charles W. Wampler
Keyword(s):  
Rigid Body ◽  
The Body ◽  
Forward Kinematics ◽  
Linear Least Squares ◽  
Geometric Problem ◽  
Quadratic Equations ◽  
Linear Least Squares Problem ◽  
Minimum Number ◽  
Parallel Link ◽  
And Robotics

This paper describes a method for finding the location of a rigid body such that N specified points of the body lie on N given planes in space. Of special interest is the case N = 6, which is the minimum number to fully constrain the body. This geometric problem arises in two seemingly disparate contexts: metrology, as a generalization of so-called “3-2-1” locating schemes; and robotics, as the forward kinematics problem for 6ES or 6SE parallel-link platform robots. For N = 6, the geometric problem can be formulated algebraically as 3 quadratic equations having, in general, eight possible solutions. We give a method for finding all eight solutions via an 8 × 8 eigenvalue problem. We also show that for N ≥ 7, the solution can be found uniquely as a linear least squares problem.

Structure and Tectonics of the Continental Slope West of Southern Vancouver Island

1974 ◽  
Vol 11 (9) ◽  
pp. 1187-1199 ◽  
Author(s):  
Sandra M. Barr
Keyword(s):  
Continental Slope ◽  
Vancouver Island ◽  
Juan De Fuca Ridge ◽  
Spreading Center ◽  
Source Depth ◽  
Northern Margin ◽  
Juan De Fuca Plate ◽  
Juan De Fuca ◽  
Diffuse Zone ◽  
Oceanic Basement

The lower continental slope west of southern Vancouver Island consists of a series of ridges formed by folding, faulting, and uplift of Cascadia Basin deposits; underlying oceanic basement, at least initially, is not involved in this deformation. The middle and upper continental slope has probably formed by the same process, combined with deposition of overlying material coming directly from the continent. This compressive deformation is postulated to be a result of underthrusting of the America Plate by the Juan de Fuca Plate. Linear magnetic anomalies produced at the Juan de Fuca spreading center can be traced under the slope for at least 40 km, further evidence for underthrusting. Anomaly source depth calculations indicate that oceanic basement dips beneath the continental slope at an angle of more than 10°. A diffuse zone of earthquake epicenters extending northeast from the northern tip of Juan de Fuca Ridge may mark the present northern margin of the Juan de Fuca Plate.

Microearthquakes at intermediate spreading-rate ridges: The Cleft segment megaplume site on the Juan de Fuca Ridge

1997 ◽  
Vol 87 (3) ◽  
pp. 684-691
Author(s):  
John A. Hildebrand ◽  
Mark A. McDonald ◽  
Spahr C. Webb
Keyword(s):  
Rift Valley ◽  
Detection Threshold ◽  
Spreading Rate ◽  
Juan De Fuca Ridge ◽  
Spreading Center ◽  
Fuca Ridge ◽  
Injection Zone ◽  
Juan De Fuca ◽  
Dike Injection ◽  
Hydrothermal Venting

Abstract We discuss models for earthquake generation at intermediate spreading-rate ridges and present results from an ocean bottom seismograph (OBS) deployment on the Cleft segment of the Juan de Fuca Ridge (JDFR). Although the Cleft segment is spreading at approximately 6 cm/yr, an intermediate spreading rate, it has no seismic activity detectable by land networks, which provide a detection threshold of ML ≧ 4, or by northeast Pacific underwater hydrophone arrays, with a detection threshold of ML ≧ 2. To monitor seismicity, four OBSs were deployed at the Cleft segment for 11 days during August 1990. These OBSs detected 34 regional earthquakes associated with adjacent transform faults. In addition, 10 local microearthquakes (ML = 0 to 1) were observed over a 10-km segment of the ridge crest. Four local events were detected sufficiently well by multiple instruments to allow their hypocenters to be determined; all these events occurred within the rift valley of the Cleft segment spreading axis. Three events lie directly beneath a linear surface zone of hydrothermal venting. This zone has been identified as the site of a seafloor volcanic eruption, dike injection, and large-scale hydrothermal venting or “megaplume” event that occurred during 1986 and 1987. These earthquakes were located at depths coincident with the dike injection zone. A possible mechanism for earthquake production might be tectonic release of stress acquired during the dike injection, either along the dike zone or along the bounding faults of the rift valley. An alternative mechanism may be stress release associated with hydrothermal activity and cooling of the dike. A fourth event was located southeast of the linear hydrothermal venting and dike injection zone, at a depth coincident with the spreading center crustal melt zone. These observations suggest that the Cleft segment may primarily experience seismic events correlated with periods of volcanic intrusion.

Interpretive gridding by anisotropic kriging

Geophysics ◽  
1993 ◽  
Vol 58 (10) ◽  
pp. 1491-1497 ◽  
Author(s):  
R. O. Hansen
Keyword(s):  
A Priori ◽  
Juan De Fuca Ridge ◽  
Aeromagnetic Data ◽  
Covariance Model ◽  
A Priori Information ◽  
Linear Features ◽  
Additional Information ◽  
Juan De Fuca ◽  
Priori Information ◽  
Minimum Curvature

Most interpolation algorithms perform poorly on data sampled along profiles crossing features whose length scales are small along the profiles but large transverse to them, such as lineaments. Rather than reproducing the linear features, these algorithms create a series of closures around the profiles. By introducing additional information into the algorithm, in particular by using an anisotropic covariance model for kriging that contains a priori information about the lineations, more realistic results can be obtained. An algorithm of this type produces a much more reasonable map of aeromagnetic data from the Cobb Offset zone of the Juan de Fuca Ridge than either minimum curvature gridding or isotropic kriging.

PETROLOGY AND PETROGENESIS OF ANDESITES FROM AXIAL SEAMOUNT, JUAN DE FUCA RIDGE

2017 ◽  
Author(s):  
Sara Renea Mills ◽  
◽  
Micheal Perfit ◽  
David A. Clague ◽  
Jennifer Brophy Paduan
Keyword(s):  
Juan De Fuca Ridge ◽  
Fuca Ridge ◽  
Juan De Fuca ◽  
Axial Seamount

scholarly journals Entrainment and bending in a major hydrothermal plume, Main Endeavour Field, Juan de Fuca Ridge

2006 ◽  
Vol 33 (19) ◽  
Author(s):  
Peter A. Rona ◽  
Karen G. Bemis ◽  
Christopher D. Jones ◽  
Darrell R. Jackson ◽  
Kyohiko Mitsuzawa ◽  
...  
Keyword(s):  
Juan De Fuca Ridge ◽  
Hydrothermal Plume ◽  
Fuca Ridge ◽  
Juan De Fuca ◽  
Main Endeavour
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