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Source process and tectonic implications of the Spanish deep-focus earthquake of March 29, 1954

Chung, Wai-Ying and Kanamori, Hiroo (1976) Source process and tectonic implications of the Spanish deep-focus earthquake of March 29, 1954. Physics of the Earth and Planetary Interiors, 13 (2). pp. 85-96. ISSN 0031-9201. https://resolver.caltech.edu/CaltechAUTHORS:20150217-133142340

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Abstract

The source process of the deep-focus Spanish earthquake of March 29, 1954 (m_b = 7.1, h = 630 km) has been studied by using seismograms recorded at teleseismic distances. Because of its unusual location, this earthquake is considered to be one of the most important earthquakes that merit detailed studies. Long-period body-wave records reveal that the earthquake is a complicated multiple event whose wave form is quite different from that of usual deep earthquakes. The total duration of P phases at teleseismic distances is as long as 40 s. This long duration may explain the considerable property damage in Granada and Malaga, Spain, which is rather rare for deep earthquakes. Using the azimuthal distribution of the differences between the arrival times of the first, the second and later P phases, the hypocenters of the later events are determined with respect to the first event. The focus of the second event is located on the vertical nodal plane of the first shock suggesting that this vertical plane is the fault plane. This fault plane which strikes in N2°E and dips 89.1°E defines a nearly vertical dip-slip fault, the block to the west moving downwards. The time interval and spatial separation between the first and the second events are 4.3 s and 19 km respectively, giving an apparent rupture velocity of 4.3 km/s which is about 74% of the S-wave velocity at the source. A third event occurred about 8.8 s after the first event and about 35.6 km from it. At least six to ten events can be identified during the whole sequence. The mechanism of some of the later events, however, seems to differ from the first two events. Synthetic seismograms are generated by superposition of a number of point sources and are matched with the observed signals to determine the seismic moment. The seismic moments of the later events are comparable to, or even larger than, that of the first. The total seismic moment is determined to be 7 · 10^(27) dyn cm while the moments of the first and the second shocks are 2.1 · 10^(26) dyn cm and 5.1 · 10^(26) dyn cm, respectively. The earthquake may represent a series of fractures in a detached piece of the lithosphere which sank rapidly into the deep mantle preserving the heterogeneity of material property at shallow depths.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0031-9201(76)90073-XDOIArticle
http://www.sciencedirect.com/science/article/pii/003192017690073XPublisherArticle
ORCID:
AuthorORCID
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 1976 Published by Elsevier B.V. Received 15 June 1976, Accepted 29 June 1976. We wish to thank John Cipar and Robert Geller for comments and suggestions for improvements of the manuscript. Discussion with Ta-hang Teng was helpful in the estimation of seismic moment. We also benefited from many discussions with K. Shimazaki. The seismograms used in our study were kindly supplied by many seismological observatories in the world, the names of which, however, are too numerous to mention here. We would like to express our sincere thanks to these observatories. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by The Air Force Office of Scientific Research under Contract No. F44620-72-C-0078. It was also partially supported by the Earth Sciences Section National Science Foundation Grant No. (EAR 76-14262).
Funders:
Funding AgencyGrant Number
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F44620-72-C-0078
NSFEAR 76-14262
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Science2758
Issue or Number:2
Record Number:CaltechAUTHORS:20150217-133142340
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150217-133142340
Official Citation:Wai-Ying Chung, Hiroo Kanamori, Source process and tectonic implications of the Spanish deep-focus earthquake of March 29, 1954, Physics of the Earth and Planetary Interiors, Volume 13, Issue 2, 1976, Pages 85-96, ISSN 0031-9201, http://dx.doi.org/10.1016/0031-9201(76)90073-X. (http://www.sciencedirect.com/science/article/pii/003192017690073X)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54877
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:17 Feb 2015 22:13
Last Modified:09 Mar 2020 13:18

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