| Abstract: | Outer-rise seismicity and dynamics are examined using inelastic models of lithospheric deformation, which allow a more realistic characterization of stress distributions and failure behaviour. We conclude that thrust- and normal-faulting outer-rise earthquakes represent substantially different states of stress within the oceanic lithosphere. Specifically, the normal-faulting events occur in response to downward plate bending, which establishes the ‘standard‘, bending-dominated state of outer-rise stress, and the thrust-faulting events occur in response to an elevated level of in-plane compression, which develops only in response to exceptional circumstances. This interpretation accounts for the observation that normal-faulting outer-rise earthquakes occur more frequently and are more widely distributed than their thrust-faulting counterparts, an observation for which the simple bending model offers no explanation. In addition, attributing both thrust- and normal-faulting outer-rise earthquakes to plate bending implies that both classes of events should occur within relatively close lateral proximity to one another because both are allegedly a manifestation of the same bending-dominated stress distribution, whereas, in reality, this is not observed. We propose that the tendency for thrust-faulting outer-rise earthquakes to exhibit greater source depths than their normal-faulting counterparts (an observation that is frequently cited in support of the bending interpretation of the former) is merely a consequence of the fact that bending-induced tension is confined to the upper lithosphere. Our model predicts that outer-rise in-plane-force variations may promote thrust-faulting outer-rise activity prior to an underthrusting interplate subduction earthquake and normal-faulting outer-rise activity following such an earthquake, but that both forms of outer-rise activity are unlikely to be associated with the same subduction earthquake. A corollary implication of our model is that subduction earthquakes are likely to be either preceded by or followed by an absence of large outer-rise earthquakes. Levels of in-plane compression necessary to generate thrust-faulting outer-rise earthquakes are attributed to stress concentrations within the subducting plate that are induced by relatively localized resistance to regionally distributed plate-driving forces. Resistance of this nature may result from either the attempted subduction of relatively buoyant (i.e. isostatically compensated) bathymetric features or the existence of strong interplate asperities. |
| Genre: | Article |
| ProdID: | 70017853 |
| Citation Author: | Mueller, S.; Spence, W.; Choy, G. L. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 72 |
| Citation Issue: | 1 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Geophysical Journal International |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 19 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Inelastic models of lithospheric stress - II. Implications for outer-rise seismicity and dynamics; 1996; Article; Journal; Geophysical Journal International; Mueller, S.; Spence, W.; Choy, G. L. |
| Citation Start Page: | 54 |
| Citation Volume: | 125 |
| Citation Year: | 1996 |
| Type: | citation/reference |
| Text: | Inelastic models of lithospheric stress - II. Implications for outer-rise seismicity and dynamics; 1996; Article; Journal; Geophysical Journal International; Mueller, S.; Spence, W.; Choy, G. L. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Mon, 1 Jan 1996 00:00 -0600 |
| Publisher: | |
