Crustal structure and seismicity of the Gorda Ridge Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2v23vw63c

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • We have determined the seismic crustal structure of the northern part of the Gorda Ridge using signals generated by explosive charges and recorded on Ocean Bottom Seismometers. The shot pattern forms two parallel lines, one on the east flank and the other along the median valley. Inversion of the travel time data and synthetic modelling of the signals resulted in two compressional velocity structures: the model for the flank indicates a 1.6 km thick upper crust characterized by high velocity gradients and 3.6 km thick lower crust characterized by a low gradient. A sharp mantle transition exists at 5.2 km depth with an upper mantle velocity of 7.6 km/sec. The median valley velocity model has a thicker high gradient upper crust of 3.0 km and a lower crust of at least 3.5 km thickness. No upper mantle velocities were detected beneath the median valley. We have also monitored the seismicity of the ridge during 15 days with two arrays of OBS and detected ~4 events/hour. Epicentral coordinates were determined for 140 earthquakes. Most of them lie within the median valley and show spatial clustering. Intraplate seismicity was also detected in the Gorda Basin with three of the earthquakes big enough to be reported by land stations. They suggest that the Gorda Plate is presently undergoing deformation. Good control over the focal depth was possible for ~80 earthquakes occurring on the ridge, and there the seismic activity appears to be pervasive throughout the upper 20 km suggesting that the the brittle lithosphere is at least this thick. From the earthquake shear-wave data we have obtained a value of 1.73 for the Vp/Vs ratio. Moments of the well constrained events derived from the spectra of the waveforms are of the order 10²⁰ dyne-cm and suggest an average fault width of 300 m. The refraction data is consistent with the earthquake results, and all the evidence suggests that a large magma chamber underlying the axis of spreading does not presently exist at shallow depths.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 8-bit Grayscale) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Submitted by Kaylee Patterson (kdpscanner@gmail.com) on 2012-05-08T19:14:11Z No. of bitstreams: 1 SolanoBorregoArielE1985.pdf: 1822023 bytes, checksum: 2c3c1a1727c35f1d0d0de6fd87d07ba3 (MD5)
  • description.provenance : Made available in DSpace on 2012-05-16T17:35:00Z (GMT). No. of bitstreams: 1 SolanoBorregoArielE1985.pdf: 1822023 bytes, checksum: 2c3c1a1727c35f1d0d0de6fd87d07ba3 (MD5) Previous issue date: 1984-09-28
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-05-16T17:35:00Z (GMT) No. of bitstreams: 1 SolanoBorregoArielE1985.pdf: 1822023 bytes, checksum: 2c3c1a1727c35f1d0d0de6fd87d07ba3 (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-05-15T19:17:59Z (GMT) No. of bitstreams: 1 SolanoBorregoArielE1985.pdf: 1822023 bytes, checksum: 2c3c1a1727c35f1d0d0de6fd87d07ba3 (MD5)

Relationships

In Administrative Set:
Last modified: 08/03/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items