uu.seUppsala University Publications
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
Source analysis of multiplet earthquakes (two case studies in Iran)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
Abstract [en]

Multiplet earthquakes are large earthquakes of similar magnitude which occur close in time in the same limited geographical area. They are not common but they considerably increase the potential hazard in the area in which they occur. This thesis studies source properties and triggering mechanisms of two sets of multiplet events in Iran, which both occurred in unexpected areas, but close to some major active fault systems. The first multiplet is an earthquake doublet (Mw 6.5 and Mw 6.4) which occurred in northwestern Iran and caused more than 300 fatalities and significant injuries. In paper I, a teleseismic body-waveform inversion was used to deduce the slip distribution pattern on the fault plane of the first mainshock. The estimated slip pattern was utilized to calculate the Coulomb stress changes on the second fault plane and on the following aftershocks. Based on this analysis, the ambiguity between the primary and auxiliary fault plane of the second mainshock could be resolved. The second set of events is a triplet (Mw 6.1 - 6.0) that occurred in eastern Iran, close to the Kerman province. In paper II, the rupture propagation patterns of the three mainshocks were analyzed using Empirical Green’s Function (EGF) deconvolution. Two different approaches were used: One, the analysis of the azimuthal variation of the apparent rupture duration based on the width of the observed relative source time functions, and the second, the analysis of along-strike rupture directivity by assessing azimuthal variations of the relative amplitude spectra. The second approach was also used to investigate the rupture directivity of the largest aftershocks in the sequence (Mw 5 - 5.5). A clear tendency for rupture propagation towards the northwest was observed for the sequence, which suggests that the regional stress field has a central role in controlling the rupture propagation direction. In paper III, the slip distribution patterns of the triplet earthquakes were analyzed using teleseismic body-waveform inversion, and the similarities and differences in the rupture processes of the three mainshocks were investigated. Using the Coulomb stress analyses, the stress interactions between the mainshocks were examined, leading to identification of the primary and auxiliary planes. Finally, we suggest that the hazard estimates in complex continental regions such as Iran need to consider the probability of multiplets, which might allow a reduction of the seismic risk associated to the occurrence of further large earthquakes subsequent to a devastating earthquake.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2020. , p. 45
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1918
Keywords [en]
Multiplet earthquakes, slip inversion, Coulomb stress, rupture directivity
National Category
Geophysics
Identifiers
URN: urn:nbn:se:uu:diva-407247ISBN: 978-91-513-0909-5 (print)OAI: oai:DiVA.org:uu-407247DiVA, id: diva2:1416110
Public defence
2020-06-12, Hambergsallen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2020-05-20 Created: 2020-03-21 Last updated: 2020-05-20
List of papers
1. Fault slip and identification of the second fault plane in the Varzeghan earthquake doublet
Open this publication in new window or tab >>Fault slip and identification of the second fault plane in the Varzeghan earthquake doublet
Show others...
2018 (English)In: Journal of Seismology, ISSN 1383-4649, E-ISSN 1573-157X, Vol. 22, no 4, p. 815-831Article in journal (Refereed) Published
Abstract [en]

An intraplate earthquake doublet, with 11-min delay between the events, devastated the city of Varzeghan in northwestern Iran on August 11, 2012. The first Mw 6.5 strike-slip earthquake, which occurred after more than 200 years of low seismicity, was followed by an Mw 6.4 oblique thrust event at an epicentral separation of about 6 km. While the first event can be associated with a distinct surface rupture, the absence of a surface fault trace and no clear aftershock signature makes it challenging to identify the fault plane of the second event. We use teleseismic body wave inversion to deduce the slip distribution in the first event. Using both P and SH waves stabilize the inversion and we further constrain the result with the surface rupture extent and the aftershock distribution. The obtained slip pattern shows two distinct slip patches with dissimilar slip directions where aftershocks avoid high-slip areas. Using the estimated slip for the first event, we calculate the induced Coulomb stress change on the nodal planes of the second event and find a preference for higher Coulomb stress on the N-S nodal plane. Assuming a simple slip model for the second event, we estimate the combined Coulomb stress changes from the two events on the focal planes of the largest aftershocks. We find that 90% of the aftershocks show increased Coulomb stress on one of their nodal planes when the N-S plane of the second event is assumed to be the correct fault plane.

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
Earthquake source estimation, Teleseismic body waves, Slip inversion, Coulomb stress changes, Asia
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-359999 (URN)10.1007/s10950-018-9734-0 (DOI)000436110300001 ()
Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2020-03-21Bibliographically approved
2. Directivity analysis of the 2017 December Kerman earthquakes in Eastern Iran
Open this publication in new window or tab >>Directivity analysis of the 2017 December Kerman earthquakes in Eastern Iran
(English)In: Journal of Seismology, ISSN 1383-4649, E-ISSN 1573-157XArticle in journal (Refereed) In press
Place, publisher, year, edition, pages
Springer
Keywords
triplet earthquake, directivity, Empirical Green's function, spectral deconvolution, restraining bend, Eastern Iran
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-407245 (URN)10.1007/s10950-020-09913-8 (DOI)
Available from: 2020-03-21 Created: 2020-03-21 Last updated: 2020-03-21
3. Fault slip and rupture properties of the December 2017 Hojedk triplet in Eastern Iran
Open this publication in new window or tab >>Fault slip and rupture properties of the December 2017 Hojedk triplet in Eastern Iran
(English)Manuscript (preprint) (Other academic)
Keywords
Fault slip, rupture properties, body-waveform inversion, Coulomb stress changes
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-407246 (URN)
Available from: 2020-03-21 Created: 2020-03-21 Last updated: 2020-04-28

Open Access in DiVA

fulltext(2061 kB)19 downloads
File information
File name FULLTEXT01.pdfFile size 2061 kBChecksum SHA-512
85769f824d35fcccacb5506eaa17185c1d053fba479684d35eb31928fc50a5cd26821a1fe63896b90012cd4e1c8301f311f4e332e71e5244184d13f555df684a
Type fulltextMimetype application/pdf

Authority records BETA

Amini, Samar

Search in DiVA

By author/editor
Amini, Samar
By organisation
Geophysics
Geophysics

Search outside of DiVA

GoogleGoogle Scholar
Total: 19 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 54 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