Slow earthquakes along oceanic fracture zones: evidence for asthenospheric flow away from hotspots?

Okal, Emile A.; Stewart, Lisa

doi:10.1016/0012-821x(82)90174-1

Cited by 76 publications

(35 citation statements)

References 33 publications

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“…Fracture zones, especially those elevated, are tectonically active fault zones undergoing displacement [18]. Fracture zones may not be just simple strike-slip faults, but zones of complex network of splays of shear faults [17], hence they are not characterized by large vigorous and frequent seismic activity, but rather intermittent small, medium and large earthquake activities, mostly generated along the transform faults and fracture zones [18,27]. In the coastal region of Ghana, this network system of splays and interfering faults occur, illustrated in Figure 3, where the St. Paul's and Romanche systems form a network and interfere as cross-faults to structurally configure southern Ghana, and cause on-going seismicity of the region.…”

Section: Discussionmentioning

confidence: 99%

“…According to Okal and Stewart [27], active submarine volcanism and seamounts are known to occur in the periphery of the Romanche system. The Romanche transform fault and fracture zone are influenced by complex asthenopheric volcanism and activities of emplacement of new oceanic crust materials, especially in the vicinity of the midocean ridge; responsible for lubricating faults, and so smoothing and slowing seismic activities along the transform faults.…”

Section: Discussionmentioning

confidence: 99%

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Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

Kutu¹

2013

IJG

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For four centuries now, southern Ghana has been known to be seismically active, and there is no clear geological explanation for the cause of the seismicity. By evaluating new field data and information with re-interpreted historical earthquake data of southern Ghana, the nature of the seismicity of southern Ghana has been elucidated. The mutual connection between the earthquake epicentres and the remote causes by Mid-Atlantic transform faults and fracture zones has been established. The seismic regions of southern Ghana have been linked separately to tectonic faults and activities of the St. Paul's and Romanche transform-fracture zone systems offshore in the Gulf of Guinea to onshore. It is concluded that the seismicity of southern Ghana is due to tectonic activities of the St. Paul's and Romanche transform-fracture systems. The Accra region earthquakes originate from reactivation of faults in the Romanche transform-fracture zone, and propagate onshore through Accra and environs. The Axim region earthquakes come from reactivated faults linked to the St Paul's fracture zone, which go through southern Cote D'Ivoire to Ghana. Seismotectonic movements along the St Paul's transform and fracture zones have quieted since 1879. But movement along the Romanche Transform fault and Fracture zone is active, causing ongoing seismicity of southern Ghana.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

Kutu¹

2013

IJG

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“…Slow earthquakes, characterized as ones whose magnitude increases with period, are often observed occurring on oceanic transform faults (Kanamori and Stewart 1976;Okal and Stewart 1982;Stein and Pelayo 1991;Choy and Boatwright 1995;Newman and Okal 1998;Perez-Campos et al 2003). Previous work has found that oceanic transform earthquakes often have lower body wave magnitudes compared to ridge and oceanic intraplate earthquakes of comparable surface wave magnitude and seismic moment.…”

Section: Introductionmentioning

confidence: 96%

Apparent Slow Oceanic Transform Earthquakes Due to Source Mechanism Bias

Schramm

Stein

2009

Seismological Research Letters

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“…Although synoptic models of fault slip behavior have been constructed [e.g., Kanamori and Cipar, 1974;Okal and Stewart, 1982;Beroza and Jordan, 19901; (2) the scaling of earthquake slip with rupture dimensions, e.g., for faults with large aspect ratios, whether slip scales observations are most comprehensive, provides a good baseline. Appendix A summarizes one interpretation of the continental data, which we will loosely refer to as the "San Andreas Fault (SAF) model," because it owes much to the abundant information from that particular fault system.…”

Section: Introductionmentioning

confidence: 99%

Slip on ridge transform faults : insights from earthquakes and laboratory experiments

Boettcher¹

2005

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The relatively simple tectonic environment of mid-ocean ridge transform fault (RTF) seismicity provides a unique opportunity for investigation of earthquake and faulting processes. We develop a scaling model that is complete in that all the seismic parameters are related to the RTF tectonic parameters. Laboratory work on the frictional stability of olivine aggregates shows that the depth extent of oceanic faulting is thermally controlled and limited by the 600°C isotherm. Slip on RTFs is primarily aseismic, only 15% of the tectonic offset is accommodated by earthquakes. Despite extensive fault areas, few large earthquakes occur on RTFs, and few aftershocks follow the large events. Standard models of seismicity, in which all earthquakes result from the same seismic triggering process, do not describe RTF earthquakes. Instead, large earthquakes appear to be preceded by an extended fault preparation process marked by abundant foreshocks within 1 hour and 15 km of the mainshocks. In our experiments normal force vibrations, such as seismic radiation from nearby earthquakes, can weaken and potentially destabilize steadily creeping faults. Integrating the rheology, geology, and seismicity of RTFs, we develop a synoptic model to better understand the spatial distribution of fault strength and stability and provide insight into slip accommodation on RTFs.

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Slow earthquakes along oceanic fracture zones: evidence for asthenospheric flow away from hotspots?

Cited by 76 publications

References 33 publications

Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

Seismic and Tectonic Correspondence of Major Earthquake Regions in Southern Ghana with Mid-Atlantic Transform-Fracture Zones

Apparent Slow Oceanic Transform Earthquakes Due to Source Mechanism Bias

Slip on ridge transform faults : insights from earthquakes and laboratory experiments

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