Item talk:Q267494

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   "@type": "Article",
   "additionalType": "Journal Article",
   "name": "Crustal structure of the Chugach Mountains, southern Alaska: A study of peg\u2010leg multiples from a low\u2010velocity zone",
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       "value": 70210210
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       "value": "10.1029/JB094iB11p16023",
       "url": "https://doi.org/10.1029/JB094iB11p16023"
     }
   ],
   "journal": {
     "@type": "Periodical",
     "name": "Journal of Geophysical Research B: Solid Earth",
     "volumeNumber": "94",
     "issueNumber": "B11"
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   "inLanguage": "en",
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   "datePublished": "1989",
   "dateModified": "2020-05-20",
   "abstract": "A seismic refraction profile recorded along the geologic strike of the Chugach Mountains in southern Alaska shows three upper crustal high\u2010velocity layers (6.9, 7.2, and 7.6 km/s) and a unique pattern of strongly focussed echelon arrivals to a distance of 225 km. The group velocity of the ensemble of echelon arrivals is 6.4 km/s. Modeling of this profile with the reflectivity method reveals that the echelon pattern is due to peg\u2010leg multiples generated from within a low\u2010velocity zone between the second and third upper crustal high\u2010velocity layers. The third high\u2010velocity layer (7.6 km/s) is underlain at 18 km depth by a pronounced low\u2010velocity zone that produces a seismic shadow zone wherein peg\u2010leg multiples are seen as echelon arrivals. The interpretation of these echelon arrivals as multiples supersedes an earlier interpretation which attributed them to successive primary reflections arising from alternating high\u2010 and low\u2010velocity layers. Synthetic seismogram modeling indicates that a low\u2010velocity zone with transitional upper and lower boundaries generates peg\u2010leg multiples as effectively as one with sharp boundaries. No\u00a0PmP\u00a0or Pn arrivals from the subducting oceanic Moho at 30 km depth beneath the western part of the line are observed on the long\u2010offset (90\u2013225 km) data. This may be due to a lower crustal waveguide whose top is the high\u2010velocity (7.6 km/s) layer and whose base is the Moho. A deep (\u223c54 km) reflector is not affected by the waveguide and has been identified in the data. Although peg\u2010leg multiples have been interpreted on some long\u2010range refraction profiles that sound to upper mantle depths, the Chugach Mountains profile is one of the few crustal refraction profiles where peg\u2010leg multiples are clearly observed. This study indicates that multiple and converted phases may be more important in seismic refraction/wide\u2010angle reflection profiles than previously recognized.",
   "description": "13 p.",
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     "name": "American Geophysical Union"
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   "author": [
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       "@type": "Person",
       "name": "Mooney, Walter D. mooney@usgs.gov",
       "givenName": "Walter D.",
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       "email": "mooney@usgs.gov",
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       "name": "Fuis, Gary S. fuis@usgs.gov",
       "givenName": "Gary S.",
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       "name": "Ambos, Elizabeth L.",
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