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Asymmetric radiation of seismic waves from an atoll: nuclear tests in French Polynesia

Geophysical Research Letters

By:
, , , , and
DOI: 10.1029/98GL51306

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Abstract

Seismic records of nuclear tests detonated in the Mururoa Atoll in French Polynesia show large unpredicted arrivals 2.2 and 4.5 seconds (X1 and X2) after the P-wave at the Australian Warramunga Array. These arrivals are not observed at the Canadian Yellowknife Array. X1 and X2 are also absent on Warramunga Array recordings of tests carried out at the Fangataufa Atoll situated 40 km SSE of Mururoa. Array analysis shows that X1 and X2 are produced within the source area. The layered crustal structure of the atoll, significant local inhomogeneities, and focusing effects due to the elongated shape and the steep flanks of the Mururoa Atoll are most likely responsible for X1 and X2. The form of Mururoa (28 × 10 km) and its East-West orientation is due to its location on the Austral Fracture Zone (AFZ). The Fangataufa Atoll on the other hand is almost circular (10 km diameter) and is unaffected by the dynamics along the AFZ. Our observations demonstrate that complicated structures in the source area can significantly alter the wave field at teleseismic distances and produce a large magnitude (mb) bias. A better understanding of the exact cause of these unusual seismic observations will only become possible, if the coordinates of the tests and information on the detailed 3-D structure of the atolls are released.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Asymmetric radiation of seismic waves from an atoll: nuclear tests in French Polynesia
Series title:
Geophysical Research Letters
DOI:
10.1029/98GL51306
Volume
25
Issue:
10
Year Published:
1998
Language:
English
Publisher:
American Geophysical Union
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geophysical Research Letters
First page:
1967
Last page:
1970
Number of Pages:
4