Interplay between faults and lava flows in construction of the upper oceanic crust : the East Pacific Rise crest 9°25′–9°58′N
Escartin, Javier E.
Soule, Samuel A.
Fornari, Daniel J.
Tivey, Maurice A.
Schouten, Hans A.
Perfit, Michael R.
MetadataShow full item record
The distribution of faults and fault characteristics along the East Pacific Rise (EPR) crest between 9°25′N and 9°58′N were studied using high-resolution side-scan sonar data and near-bottom bathymetric profiles. The resulting analysis shows important variations in the density of deformational features and tectonic strain estimates at young seafloor relative to older, sediment-covered seafloor of the same spreading age. We estimate that the expression of tectonic deformation and associated strain on “old” seafloor is ~5 times greater than that on “young” seafloor, owing to the frequent fault burial by recent lava flows. Thus the unseen, volcanically overprinted tectonic deformation may contribute from 30% to 100% of the ~300 m of subsidence required to fully build up the extrusive pile (Layer 2A). Many longer lava flows (greater than ~1 km) dam against inward facing fault scarps. This limits their length at distances of 1–2 km, which are coincident with where the extrusive layer acquires its full thickness. More than 2% of plate separation at the EPR is accommodated by brittle deformation, which consists mainly of inward facing faults (~70%). Faulting at the EPR crest occurs within the narrow, ~4 km wide upper crust that behaves as a brittle lid overlying the axial magma chamber. Deformation at greater distances off axis (up to 40 km) is accommodated by flexure of the lithosphere due to thermal subsidence, resulting in ~50% inward facing faults accommodating ~50% of the strain. On the basis of observed burial of faults by lava flows and damming of flows by fault scarps, we find that the development of Layer 2A is strongly controlled by low-relief growth faults that form at the ridge crest and its upper flanks. In turn, those faults have a profound impact on how lava flows are distributed along and across the ridge crest.
Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q06005, doi:10.1029/2006GC001399.
Showing items related by title, author, creator and subject.
Thermal-mechanical behavior of oceanic transform faults : implications for the spatial distribution of seismicity Roland, Emily C.; Behn, Mark D.; Hirth, Greg (American Geophysical Union, 2010-07-01)To investigate the spatial distribution of earthquakes along oceanic transform faults, we utilize a 3-D finite element model to calculate the mantle flow field and temperature structure associated with a ridge-transform-ridge ...
Seismic velocity constraints on the material properties that control earthquake behavior at the Quebrada-Discovery-Gofar transform faults, East Pacific Rise Roland, Emily C.; Lizarralde, Daniel; McGuire, Jeffrey J.; Collins, John A. (American Geophysical Union, 2012-11-17)Mid-ocean ridge transform faults (RTFs) vary strongly along strike in their ability to generate large earthquakes. This general observation suggests that local variations in material properties along RTFs exert a primary ...
Imaging along-strike variations in mechanical properties of the Gofar transform fault, East Pacific Rise Froment, B.; McGuire, Jeffrey J.; van der Hilst, R. D.; Gouedard, P.; Roland, Emily C.; Zhang, H.; Collins, John A. (John Wiley & Sons, 2014-09-23)A large part of global plate motion on mid-ocean ridge transform faults (RTFs) is not accommodated as major earthquakes. When large earthquakes do occur, they often repeat quasiperiodically. We focus here on the high slip ...