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High frequency seismic waves and slab structures beneath Italy

Sun, Daoyuan and Miller, Meghan S. and Agostinetti, Nicola Piana and Asimow, Paul D. and Li, Dunzhu (2014) High frequency seismic waves and slab structures beneath Italy. Earth and Planetary Science Letters, 391 . pp. 212-223. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20140508-135028711

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Abstract

Tomographic images indicate a complicated subducted slab structure beneath the central Mediterranean where gaps in fast velocity anomalies in the upper mantle are interpreted as slab tears. The detailed shape and location of these tears are important for kinematic reconstructions and understanding the evolution of the subduction system. However, tomographic images, which are produced by smoothed, damped inversions, will underestimate the sharpness of the structures. Here, we use the records from the Italian National Seismic Network (IV) to study the detailed slab structure. The waveform records for stations in Calabria show large amplitude, high frequency (f>5 Hz) late arrivals with long coda after a relatively low-frequency onset for both P and S waves. In contrast, the stations in the southern and central Apennines lack such high frequency arrivals, which correlate spatially with the central Apennines slab window inferred from tomography and receiver function studies. Thus, studying the high frequency arrivals provides an effective way to investigate the structure of slab and detect possible slab tears. The observed high frequency arrivals in the southern Italy are the strongest for events from 300 km depth and greater whose hypocenters are located within the slab inferred from fast P-wave velocity perturbations. This characteristic behavior agrees with previous studies from other tectonic regions, suggesting the high frequency energy is generated by small scale heterogeneities within the slab which act as scatterers. Furthermore, using a 2-D finite difference (FD) code, we calculate synthetic seismograms to search for the scale, shape and velocity perturbations of the heterogeneities that may explain features observed in the data. Our preferred model of the slab heterogeneities beneath the Tyrrhenian Sea has laminar structure parallel to the slab dip and can be described by a von Kármán function with a down-dip correlation length of 10 km and 0.5 km in thickness with ∼2.5% V_p fluctuations within the slab. This suggests that the heterogeneities are inherited from the melt shear bands formed during the original formation of the oceanic lithosphere near the mid-ocean ridge.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2014.01.034DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X14000508PublisherArticle
ORCID:
AuthorORCID
Sun, Daoyuan0000-0003-4461-4664
Asimow, Paul D.0000-0001-6025-8925
Li, Dunzhu0000-0003-3149-0236
Additional Information:© 2014 Elsevier B.V. Received 31 October 2013. Received in revised form 18 January 2014. Accepted 24 January 2014. Available online 19 February 2014. Editor: P. Shearer. The authors would like to thank the editor and two reviewers for their suggestions and comments. We also thank Don Anderson, Don Helmberger, and The-Ru Alex Song for stimulating conversations and communications. This work was supported by funding provided by NSF CAREER award (EAR-1054638) and USC postdoctoral scholar research grant. A special thanks to Dr. Giulio Selvaggi, director of INGV-CNT, and Centro Nazionale Terremoti for providing the data. NPA research is supported by Science Foundation Ireland & the Marie-Curie Action COFUND under Grant Number 11/SIRG/E2174.
Funders:
Funding AgencyGrant Number
NSFEAR-1054638
University of Southern CaliforniaUNSPECIFIED
Science Foundation, IrelandUNSPECIFIED
Marie Curie Fellowship11/SIRG/E2174
Subject Keywords:high frequency waves; small-scale heterogeneities; slab beneath Italy
Record Number:CaltechAUTHORS:20140508-135028711
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140508-135028711
Official Citation:Daoyuan Sun, Meghan S. Miller, Nicola Piana Agostinetti, Paul D. Asimow, Dunzhu Li, High frequency seismic waves and slab structures beneath Italy, Earth and Planetary Science Letters, Volume 391, 1 April 2014, Pages 212-223, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2014.01.034. (http://www.sciencedirect.com/science/article/pii/S0012821X14000508)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45612
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:08 May 2014 21:39
Last Modified:02 Oct 2017 19:20

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