Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone
Abstract Geophysical and rheological work below the subduction seismogenic zone suggest that elevated pore fluid pressures (Pfs) may facilitate slow slip and tremor. However, quantification of Pf and its variation in this environment remain indirect and incomplete. We examine brittle‐frictional defo...
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Wiley
2022-06-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1029/2022GL098862 |
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| author | C. B. Condit M. E. French |
| author_facet | C. B. Condit M. E. French |
| author_sort | C. B. Condit |
| collection | DOAJ |
| description | Abstract Geophysical and rheological work below the subduction seismogenic zone suggest that elevated pore fluid pressures (Pfs) may facilitate slow slip and tremor. However, quantification of Pf and its variation in this environment remain indirect and incomplete. We examine brittle‐frictional deformation within metasedimentary rocks from an exhumed subduction zone. Here, penetrative foliation formed under viscous deformation conditions by pressure‐solution creep at 0.9 GPa, 300–350°C, and differential stresses <35 MPa. Three sets of crack‐seal veins, precipitated at peak subduction temperatures, cross‐cut this foliation. Mechanical inversions of these veins indicate they formed within a single stress field orientation with foliation, but at different magnitudes of differential stress. These deformation structures reveal near‐lithostatic Pf that fluctuated in time by perhaps only ∼4 MPa, resulting in cyclic mode I and shear fracturing and viscous flow, and support slow slip and tremor mechanisms that require or are enhanced by high Pf and low differential stress. |
| format | Article |
| id | doaj-art-6fbc4392af544ea3af7789ada4a0b196 |
| institution | Kabale University |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2022-06-01 |
| publisher | Wiley |
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| series | Geophysical Research Letters |
| spelling | doaj-art-6fbc4392af544ea3af7789ada4a0b1962025-01-22T14:38:16ZengWileyGeophysical Research Letters0094-82761944-80072022-06-014912n/an/a10.1029/2022GL098862Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic ZoneC. B. Condit0M. E. French1University of Washington Seattle WA USARice University Houston TX USAAbstract Geophysical and rheological work below the subduction seismogenic zone suggest that elevated pore fluid pressures (Pfs) may facilitate slow slip and tremor. However, quantification of Pf and its variation in this environment remain indirect and incomplete. We examine brittle‐frictional deformation within metasedimentary rocks from an exhumed subduction zone. Here, penetrative foliation formed under viscous deformation conditions by pressure‐solution creep at 0.9 GPa, 300–350°C, and differential stresses <35 MPa. Three sets of crack‐seal veins, precipitated at peak subduction temperatures, cross‐cut this foliation. Mechanical inversions of these veins indicate they formed within a single stress field orientation with foliation, but at different magnitudes of differential stress. These deformation structures reveal near‐lithostatic Pf that fluctuated in time by perhaps only ∼4 MPa, resulting in cyclic mode I and shear fracturing and viscous flow, and support slow slip and tremor mechanisms that require or are enhanced by high Pf and low differential stress.https://doi.org/10.1029/2022GL098862slow slipsubductionpore fluid pressurefracture mechanics |
| spellingShingle | C. B. Condit M. E. French Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone Geophysical Research Letters slow slip subduction pore fluid pressure fracture mechanics |
| title | Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone |
| title_full | Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone |
| title_fullStr | Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone |
| title_full_unstemmed | Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone |
| title_short | Geologic Evidence of Lithostatic Pore Fluid Pressures at the Base of the Subduction Seismogenic Zone |
| title_sort | geologic evidence of lithostatic pore fluid pressures at the base of the subduction seismogenic zone |
| topic | slow slip subduction pore fluid pressure fracture mechanics |
| url | https://doi.org/10.1029/2022GL098862 |
| work_keys_str_mv | AT cbcondit geologicevidenceoflithostaticporefluidpressuresatthebaseofthesubductionseismogeniczone AT mefrench geologicevidenceoflithostaticporefluidpressuresatthebaseofthesubductionseismogeniczone |