Time-dependent seismic tomography and its application to the Coso geothermal area, 1996-2006

PDF Version Also Available for Download.

Description

Measurements of temporal changes in Earth structure are commonly determined using localearthquake tomography computer programs that invert multiple seismic-wave arrival time data sets separately and assume that any differences in the structural results arise from real temporal variations. This assumption is dangerous because the results of repeated tomography experiments would differ even if the structure did not change, simply because of variation in the seismic ray distribution caused by the natural variation in earthquake locations. Even if the source locations did not change (if only explosion data were used, for example), derived structures would inevitably differ because of observational errors. ... continued below

Physical Description

387-390

Creation Information

Julian, B.R.; Foulger, G.R. & Monastero, F. April 1, 2008.

Context

This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. It has been viewed 31 times . More information about this article can be viewed below.

Who

People and organizations associated with either the creation of this article or its content.

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this article. Follow the links below to find similar items on the Digital Library.

Description

Measurements of temporal changes in Earth structure are commonly determined using localearthquake tomography computer programs that invert multiple seismic-wave arrival time data sets separately and assume that any differences in the structural results arise from real temporal variations. This assumption is dangerous because the results of repeated tomography experiments would differ even if the structure did not change, simply because of variation in the seismic ray distribution caused by the natural variation in earthquake locations. Even if the source locations did not change (if only explosion data were used, for example), derived structures would inevitably differ because of observational errors. A better approach is to invert multiple data sets simultaneously, which makes it possible to determine what changes are truly required by the data. This problem is similar to that of seeking models consistent with initial assumptions, and techniques similar to the “damped least squares” method can solve it. We have developed a computer program, dtomo, that inverts multiple epochs of arrival-time measurements to determine hypocentral parameters and structural changes between epochs. We shall apply this program to data from the seismically active Coso geothermal area, California, in the near future. The permanent network operated there by the US Navy, supplemented by temporary stations, has provided excellent earthquake arrival-time data covering a span of more than a decade. Furthermore, structural change is expected in the area as a result of geothermal exploitation of the resource. We have studied the period 1996 through 2006. Our results to date using the traditional method show, for a 2-km horizontal grid spacing, an irregular strengthening with time of a negative VP/VS anomaly in the upper ~ 2 km of the reservoir. This progressive reduction in VP/VS results predominately from an increase of VS with respect to VP. Such a change is expected to result from effects of geothermal operations such as decreasing fluid pressure and the drying of argillaceous minerals such as illite.

Physical Description

387-390

Source

  • Journal Volume: SGP-TR-185; Conference: Thirty-Third Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 28-30, 2008

Language

Item Type

Identifier

Unique identifying numbers for this article in the Digital Library or other systems.

  • Report No.: Final Report supplement 1
  • Grant Number: FG36-06GO16058
  • Office of Scientific & Technical Information Report Number: 926250
  • Archival Resource Key: ark:/67531/metadc902193

Collections

This article is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this article?

When

Dates and time periods associated with this article.

Creation Date

  • April 1, 2008

Added to The UNT Digital Library

  • Sept. 27, 2016, 1:39 a.m.

Usage Statistics

When was this article last used?

Yesterday: 0
Past 30 days: 3
Total Uses: 31

Interact With This Article

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

International Image Interoperability Framework

IIF Logo

We support the IIIF Presentation API

Julian, B.R.; Foulger, G.R. & Monastero, F. Time-dependent seismic tomography and its application to the Coso geothermal area, 1996-2006, article, April 1, 2008; United States. (digital.library.unt.edu/ark:/67531/metadc902193/: accessed September 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.