Long-Term Offshore Borehole Fluid-Pressure Monitoring at the Northern Cascadia Subduction Zone and Inferences Regarding the State of Megathrust Locking

Simple item page
dc.contributor.authorDavis, Earl E.
dc.contributor.authorSun, Tianhaozhe
dc.contributor.authorHeesemann, Martin
dc.contributor.authorBecker, Keir
dc.contributor.authorSchlesinger, Angela
dc.date.accessioned2023-06-12T03:55:42Z
dc.date.available2023-06-12T03:55:42Z
dc.date.copyright2023en_US
dc.date.issued2023-06-06
dc.description.abstractThe Cascadia subduction megathrust off the Pacific Northwest follows an “end member” seismogenic behavior, producing large (up to moment magnitude 9) but infrequent (every several hundred years) earthquakes and tsunamis. Crustal deformation associated with the ongoing plate convergence has been characterized by land-based geodetic observations, but the state of locking across the full breadth of the seismogenic fault is poorly constrained. We report results of offshore monitoring of borehole fluid pressure, as a proxy for formation volumetric strain, at a site ∼20 km landward of the Cascadia subduction deformation front since 2010. The multi-depth pressure records were plagued by hydrologic noise, but noise at the deepest monitoring level (303 m sub-seafloor) abated in 2015. Subsequently, including at the times of regional large earthquakes that caused significant dynamic stressing, no persistent pressure transients are present above a threshold of 0.08 kPa imposed by unremovable oceanographic signals, corresponding to a strain detection limit of ∼16 nanostrain. Simple dislocation models using local megathrust geometry suggest a resolvable slip of <1 cm along a trench-normal corridor beneath the borehole for a range of slip-patch dimensions. A large slip patch can be well resolved even at considerable along-strike distances from the borehole; for instance, ∼10 cm slip is detectable over a 200-km strike range for a slip-patch radius of ∼50 km. This high sensitivity for detecting slip, along with the lack of observed events, stands in stark contrast to observations at other subduction zones, and suggests that the Northern Cascadia megathrust is most likely fully locked.en_US
dc.description.reviewstatusRevieweden_US
dc.description.scholarlevelFacultyen_US
dc.description.sponsorshipNational Science Board. Grant Number: OCE-1259718 U.S. National Science Foundationen_US
dc.identifier.citationDavis, E. E., Sun, T., Heesemann, M., Becker, K., & Schlesinger, A. (2023). Long-term offshore borehole fluid-pressure monitoring at the northern Cascadia subduction zone and inferences regarding the state of megathrust locking. Geochemistry, Geophysics, Geosystems, 24, e2023GC010910. https://doi.org/10.1029/2023GC010910en_US
dc.identifier.urihttps://doi.org/10.1029/2023GC010910
dc.identifier.urihttp://hdl.handle.net/1828/15161
dc.language.isoenen_US
dc.publisherGeochemistry, Geophysics, Geosystemsen_US
dc.subjectsubduction megathrust lockingen_US
dc.subjectoffshore geodesyen_US
dc.subjectfluid pressure monitoringen_US
dc.subjectborehole observatoryen_US
dc.subjectIODPen_US
dc.subjectevent detection thresholden_US
dc.subjectresolvable slipen_US
dc.titleLong-Term Offshore Borehole Fluid-Pressure Monitoring at the Northern Cascadia Subduction Zone and Inferences Regarding the State of Megathrust Lockingen_US
dc.typeArticleen_US

Files

Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Heesemann_Geochemistry_Geophys._Geosystems_2023.pdf
Size:
5.89 MB
Format:
Adobe Portable Document Format
Description:
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
2 KB
Format:
Item-specific license agreed upon to submission
Description:
Download

Collections

Faculty Publications (BioMed Central & Faculty of Science)
 
University of Victoria Libraries

We acknowledge and respect the Lək̓ʷəŋən (Songhees and Esquimalt) Peoples on whose territory the university stands, and the Lək̓ʷəŋən and W̱SÁNEĆ Peoples whose historical relationships with the land continue to this day.