SEASAT geoid anomalies and the Macquarie Ridge complex
The seismically active Macquarie Ridge complex forms the Pacific-India plate boundary between New Zealand and the Pacific-Antarctic spreading center. The Late Cenozoic deformation of New Zealand and focal mechanisms of recent large earthquakes in the Macquarie Ridge complex appear consistent with th...
| Published in: | Physics of the Earth and Planetary Interiors |
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| Main Authors: | , |
| Other Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Elsevier
1985
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| Subjects: | |
| Online Access: | https://hdl.handle.net/2027.42/25729 http://www.sciencedirect.com/science/article/B6V6S-472SHPH-1W/2/557a8341ebe5913846841c30ede12958 https://doi.org/10.1016/0031-9201(85)90122-0 |
| Summary: | The seismically active Macquarie Ridge complex forms the Pacific-India plate boundary between New Zealand and the Pacific-Antarctic spreading center. The Late Cenozoic deformation of New Zealand and focal mechanisms of recent large earthquakes in the Macquarie Ridge complex appear consistent with the current plate tectonic models. These models predict a combination of strike-slip and convergent motion in the northern Macquarie Ridge, and strike-slip motion in the southern part. The Hjort trench is the southernmost expression of the Macquarie Ridge complex. Regional considerations of the magnetic lineations imply that some oceanic crust may have been consumed at the Hjort trench. Although this arcuate trench seems inconsistent with the predicted strike-slip setting, a deep trough also occurs in the Romanche fracture zone.Geoid anomalies observed over spreading ridges, subduction zones, and fracture zones are different. Therefore, geoid anomalies may be diagnostic of plate boundary type. We use SEASAT data to examine the Macquarie Ridge complex and find that the geoid anomalies for the northern Hjort trench region are different from the geoid anomalies for the Romanche trough. The Hjort trench region is characterized by an oblique subduction zone geoid anomaly, e.g., the Aleutian-Komandorski region. Also, limited first-motion data for the large 1924 earthquake that occurred in the northern Hjort trench suggest a thrust focal mechanism. We conclude that subduction is occurring at the Hjort trench. The existence of active subduction in this area implies that young oceanic lithosphere can subduct beneath older oceanic lithosphere. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/25729/1/0000286.pdf |
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