JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

S (Solid Earth Sciences) » S-CG Complex & General

[S-CG66] [EE] Shallow and intermediate depth intraslab earthquakes: seismogenesis and rheology of the slab

Tue. May 23, 2017 1:45 PM - 3:15 PM A07 (Tokyo Bay Makuhari Hall)

convener:Tomohiro Ohuchi(Geodynamics Research Center, Ehime University), Saeko Kita(Department of Earth and Planetary Systems Science, Hiroshima University), Brent G Delbridge(Berkeley Seismological Lab), Ikuo Katayama(Department of Earth and Planetary Systems Science, Hiroshima University), Chairperson:Saeko Kita(Department of Earth and Planetary Systems Science, Hiroshima University), Chairperson:Brent Delbridge(Berkeley Seismological Lab)

2:30 PM - 2:45 PM

[SCG66-10] Controlled-source EM data constrain porosity and fluid budget of the outer rise and forearc slope offshore Nicaragua

*Samer Naif1, Kerry Key2, Steven Constable2, Rob L Evans3 (1.Lamont Doherty Earth Observatory, 2.Scripps Institution of Oceanography, 3.Woods Hole Oceanographic Institution)

Controlled-source electromagnetic (CSEM) soundings provide important constraints on the electrical structure of the uppermost oceanic lithosphere. Since the conductivity signature of porous media is strongly dependent on the presence of saline fluids, CSEM data can be used to quantify porosity. Here, we present results from the Middle America Trench offshore Nicaragua, the first CSEM survey across a subduction margin. The results document the capacity of CSEM observations to image a variety of relevant convergent margin processes, including fluid pathways associated with faulting and subducted sediments along the plate interface. In the outer rise, several sub-vertical conductive channels occur along the trace of bending faults. This suggests localized hydration and the development of a heterogeneous pattern of crustal alteration. Our porosity estimates constrain the fluid budget of the incoming crust, indicating significantly more pore fluids are subducted than previously thought. Seismic implications will be discussed.