uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Focusing patterns of seismicity with relocation and collapsing
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Show others and affiliations
2016 (English)In: Journal of Seismology, ISSN 1383-4649, E-ISSN 1573-157X, Vol. 20, no 3, 771-786 p.Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Seismicity is generally concentrated on faults or in fault zones of varying, sometimes complex geometry. An earthquake catalog, compiled over time, contains useful information about this geometry, which can help understanding the tectonics of a region. Interpreting the geometrical distribution of events in a catalog is often complicated by the diffuseness of the earthquake locations. Here, we explore a number of strategies to reduce this diffuseness and hence simplify the seismicity pattern of an earthquake catalog. These strategies utilize information about event locations contained in their overall catalog distribution. They apply this distribution as an a priori constraint on relocations of the events, or as an attractor for each individual event in a collapsing scheme, and thereby focus the locations. The latter strategy is not a relocation strategy in a strict sense, although event foci are moved, because the movements are not driven by data misfit. Both strategies simplify the seismicity pattern of the catalog and may help to interpret it. A synthetic example and a real-data example from an aftershock sequence in south west Iceland are presented to demonstrate application of the strategies. Entropy is used to quantify their effect.

Place, publisher, year, edition, pages
2016. Vol. 20, no 3, 771-786 p.
Keyword [en]
Probability distributions, Clustering, Seismicity, Image processing
National Category
Geophysics
Identifiers
URN: urn:nbn:se:uu:diva-299849DOI: 10.1007/s10950-016-9556-xISI: 000378773800004OAI: oai:DiVA.org:uu-299849DiVA: diva2:950275
Available from: 2016-07-29 Created: 2016-07-28 Last updated: 2017-08-01Bibliographically approved
In thesis
1. Location and Relocation of Seismic Sources
Open this publication in new window or tab >>Location and Relocation of Seismic Sources
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation is a comprehensive summary of four papers on the development and application of new strategies for locating tremor and relocating events in earthquake catalogs.

In the first paper, two new strategies for relocating events in a catalog are introduced. The seismicity pattern of an earthquake catalog is often used to delineate seismically active faults. However, the delineation is often hindered by the diffuseness of earthquake locations in the catalog. To reduce the diffuseness and simplify the seismicity pattern, a relocation and a collapsing method are developed and applied. The relocation method uses the catalog event density as an a priori constraint for relocations in a Bayesian inversion. The catalog event density is expressed in terms of the combined probability distribution of all events in the catalog. The collapsing method uses the same catalog density as an attractor for focusing the seismicity in an iterative scheme. These two strategies are applied to an aftershock sequence after a pair of earthquakes which occurred in southwest Iceland, 2008. The seismicity pattern is simplified by application of the methods and the faults of the mainshocks are delineated by the reworked catalog.

In the second paper, the spatial distribution of seismicity of the Hengill region, southwest Iceland is analyzed. The relocation and collapsing methods developed in the first paper and a non-linear relocation strategy using empirical traveltime tables are used to process a catalog collected by the Icelandic Meteorological Office. The reworked catalog reproduces details of the spatial distribution of seismicity that independently emerges from relative relocations of a small subset of the catalog events. The processed catalog is then used to estimate the depth to the brittle-ductile transition. The estimates show that in general the northern part of the area, dominated by volcanic processes, has a shallower depth than the southern part, where tectonic deformation predominates.

In the third and the fourth papers, two back-projection methods using inter-station cross correlations are proposed for locating tremor sources. For the first method, double correlations, defined as the cross correlations of correlations from two station pairs sharing a common reference station, are back projected. For the second method, the products of correlation envelopes from a group of stations sharing a common reference station are back projected. Back projecting these combinations of correlations, instead of single correlations, suppresses random noise and reduces the strong geometrical signature caused by the station configuration. These two methods are tested with volcanic tremor at Katla volcano, Iceland. The inferred source locations agree with surface observations related to volcanic events which occurred during the tremor period.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 73 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1532
Keyword
Earthquake location, Earthquake relocation, Tremor location, Bayesian inversion, Correlation, Earthquake catalog, Iceland, Seismicity, Interferometry, Inverse theory, Volcanic tremor
National Category
Geophysics
Research subject
Geophysics with specialization in Seismology
Identifiers
urn:nbn:se:uu:diva-327038 (URN)978-91-513-0013-9 (ISBN)
Public defence
2017-09-15, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2017-08-23 Created: 2017-08-01 Last updated: 2017-09-08

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Li, Ka LokGudmundsson, ÓlafurTryggvason, AriBödvarsson, Reynir
By organisation
Geophysics
In the same journal
Journal of Seismology
Geophysics

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 267 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf