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Estimation of seismic attenuation from ambient noise coda waves; application to the Hellenic subduction zone

Pratul Ranjan and Laurent Stehly
Estimation of seismic attenuation from ambient noise coda waves; application to the Hellenic subduction zone
Bulletin of the Seismological Society of America (February 2024) Pre-Issue Publication

Abstract

The decay of surface-wave coda in ambient noise cross correlations can facilitate the estimation of seismic attenuation. The coda quality factor (Q (sub c) ) can be measured in longer period bands using ambient noise cross correlations, which is the main advantage of using them over earthquakes. The classic model of Aki and Chouet (1975) has been applied previously to estimate coda Q in the Alps using ambient noise cross correlations. The Alps represents an ideal environment for ambient noise study, because it has very high and near-uniform station density, and the region is away from oceanic noise sources. However, many regions around the world do not have uniform station density and may be seismically more active than the Alps. One such region is the Hellenic subduction zone (HSZ), because it has a high rate of seismicity, sparser station coverage, and is surrounded by seas from outside and within. In this study, we estimate ambient seismic noise Q (sub c) in 2.5-5, 5-10, and 10-20 s period bands for the HSZ, which did not exist previously. Then, we mitigate the effects of lapse time and window length, distance, azimuth, as well as the number of stacked days on the Q (sub c) . Mapping of Q (sub c) measurements in such a geographically heterogeneous setting poses additional challenges, which we solve using a novel approach that adaptively selects paths based on their lengths and azimuthal distribution. The major tectonic zones are identified in the resulting Q (sub c) maps in the form of low Q (sub c) such as the North Anatolian fault, the Kefalonia transform zone, the Gulf of Corinth, the volcanic centers, and so on. The results also show a good correlation with large topographical features such as the Hellenides and the Thessalian plains, which have also been noticed from Q (sub c) analysis in other parts of the world.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: Pre-Issue Publication
Title: Estimation of seismic attenuation from ambient noise coda waves; application to the Hellenic subduction zone
Affiliation: National Geophysical Research Institute, Hyderabad, India
Published: 20240228
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 107
Accession Number: 2024-022096
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch maps
N34°00'00" - N42°00'00", E21°00'00" - E30°00'00"
Secondary Affiliation: Universite Grenoble Alpes, Institut des Sciences de la Terre, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2024, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2024
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