Browse
Submit Data
Databases
API
Help

Dataset Information

28 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Fluid pressure and shear zone development over the locked to slow slip region in Cascadia.

ABSTRACT: At subduction zones, the deep seismogenic transition from a frictionally locked to steady sliding interface is thought to primarily reflect changes in rheology and fluid pressure and is generally located offshore. The development of fluid pressures within a seismic low-velocity layer (LVL) remains poorly constrained due to the scarcity of dense, continuous onshore-offshore broadband seismic arrays. We image the subducting Juan de Fuca oceanic plate in northern Cascadia using onshore-offshore teleseismic data and find that the signature of the LVL does not extend into the locked zone. Thickening of the LVL down dip where viscous creep dominates suggests that it represents the development of an increasingly thick and fluid-rich shear zone, enabled by fluid production in subducting oceanic crust. Further down dip, episodic tremor, and slip events occur in a region inferred to have locally increased fluid pressures, in agreement with electrical resistivity structure and numerical models of fault slip.

SUBMITTER: Audet P

PROVIDER: S-EPMC5846282 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Slip bursts during coalescence of slow slip events in Cascadia.

Project description:Both laboratory experiments and dynamic simulations suggest that earthquakes can be preceded by a precursory phase of slow slip. Observing processes leading to an acceleration or spreading of slow slip along faults is therefore key to understand the dynamics potentially leading to seismic ruptures. Here, we use continuous GPS measurements of the ground displacement to image the daily slip along the fault beneath Vancouver Island during a slow slip event in 2013. We image the coalescence of three originally distinct slow slip fronts merging together. We show that during coalescence phases lasting for 2 to 5 days, the rate of energy (moment) release significantly increases. This observation supports the view proposed by theoretical and experimental studies that the coalescence of slow slip fronts is a possible mechanism for initiating earthquakes.

| S-EPMC7195424 | biostudies-literature

Cascadia low frequency earthquakes at the base of an overpressured subduction shear zone.

Project description:In subduction zones, landward dipping regions of low shear wave velocity and elevated Poisson's ratio, which can extend to at least 120 km depth, are interpreted to be all or part of the subducting igneous oceanic crust. This crust is considered to be overpressured, because fluids within it are trapped beneath an impermeable seal along the overlying inter-plate boundary. Here we show that during slow slip on the plate boundary beneath southern Vancouver Island, low frequency earthquakes occur immediately below both the landward dipping region of high Poisson's ratio and a 6-10 km thick shear zone revealed by seismic reflections. The plate boundary here either corresponds to the low frequency earthquakes or to the anomalous elastic properties in the lower 3-5 km of the shear zone immediately above them. This zone of high Poisson's ratio, which approximately coincides with an electrically conductive layer, can be explained by slab-derived fluids trapped at near-lithostatic pore pressures.

| S-EPMC7398906 | biostudies-literature

An exponential build-up in seismic energy suggests a months-long nucleation of slow slip in Cascadia.

Project description:Slow slip events result from the spontaneous weakening of the subduction megathrust and bear strong resemblance to earthquakes, only slower. This resemblance allows us to study fundamental aspects of nucleation that remain elusive for classic, fast earthquakes. We rely on machine learning algorithms to infer slow slip timing from statistics of seismic waveforms. We find that patterns in seismic power follow the 14-month slow slip cycle in Cascadia, arguing in favor of the predictability of slow slip rupture. Here, we show that seismic power exponentially increases as the slowly slipping portion of the subduction zone approaches failure, a behavior that shares a striking similarity with the increase in acoustic power observed prior to laboratory slow slip events. Our results suggest that the nucleation phase of Cascadia slow slip events may last from several weeks up to several months.

| S-EPMC7435189 | biostudies-literature

Fault zone heterogeneities explain depth-dependent pattern and evolution of slow earthquakes in Cascadia.

Project description:Slow earthquakes including tremor and slow-slip events are recent additions to the conventional earthquake family and have a close link to megathrust earthquakes. Slow earthquakes along the Cascadia subduction zone display a diverse behavior at different spatiotemporal scales and an intriguing increase of events frequency with depth. However, what causes such variability, especially the depth-dependent behavior is not well understood. Here we build on a heterogeneous asperities-in-matrix fault model that incorporates differential pore pressure in a rate-and-state friction framework to investigate the underlying processes of the observed episodic tremor and slow-slip (ETS) variability. We find that the variations of effective normal stress (pore pressure) is one important factor in controlling ETS behavior. Our model reproduces the full complexity of ETS patterns and the depth-frequency scaling that agree quantitatively well with observations, suggesting that fault zone heterogeneities can be one viable mechanism to explain a broad spectrum of transient fault behaviors.

| S-EPMC8010077 | biostudies-literature

Earthquake swarms and slow slip on a sliver fault in the Mexican subduction zone.

Project description:The Mexican subduction zone is an ideal location for studying subduction processes due to the short trench-to-coast distances that bring broad portions of the seismogenic and transition zones of the plate interface inland. Using a recently generated seismicity catalog from a local network in Oaxaca, we identified 20 swarms of earthquakes (M < 5) from 2006 to 2012. Swarms outline what appears to be a steeply dipping structure in the overriding plate, indicative of an origin other than the plate interface. This steeply dipping structure corresponds to the northern boundary of the Xolapa terrane. In addition, we observed an interesting characteristic of slow slip events (SSEs) where they showed a shift from trenchward motion toward an along-strike direction at coastal GPS sites. A majority of the swarms were found to correspond in time to the along-strike shift. We propose that swarms and SSEs are occurring on a sliver fault that allows the oblique convergence to be partitioned into trench-perpendicular motion on the subduction interface and trench-parallel motion on the sliver fault. The resistivity structure surrounding the sliver fault suggests that SSEs and swarms of earthquakes occur due to high fluid content in the fault zone. We propose that the sliver fault provides a natural pathway for buoyant fluids attempting to migrate upward after being released from the downgoing plate. Thus, sliver faults could be responsible for the downdip end of the seismogenic zone by creating drier conditions on the subduction interface trenchward of the sliver fault, promoting fast-slip seismogenic rupture behavior.

| S-EPMC6462109 | biostudies-literature

Shallow very-low-frequency earthquakes accompany slow slip events in the Nankai subduction zone.

Project description:Recent studies of slow earthquakes along plate boundaries have shown that tectonic tremor, low-frequency earthquakes, very-low-frequency events (VLFEs), and slow-slip events (SSEs) often accompany each other and appear to share common source faults. However, the source processes of slow events occurring in the shallow part of plate boundaries are not well known because seismic observations have been limited to land-based stations, which offer poor resolution beneath offshore plate boundaries. Here we use data obtained from seafloor observation networks in the Nankai trough, southwest of Japan, to investigate shallow VLFEs in detail. Coincident with the VLFE activity, signals indicative of shallow SSEs were detected by geodetic observations at seafloor borehole observatories in the same region. We find that the shallow VLFEs and SSEs share common source regions and almost identical time histories of moment release. We conclude that these slow events arise from the same fault slip and that VLFEs represent relatively high-frequency fluctuations of slip during SSEs.

| S-EPMC5852141 | biostudies-literature

Effects of episodic slow slip on seismicity and stress near a subduction-zone megathrust.

Project description:Slow slip phenomena deep in subduction zones reveal cyclic processes downdip of locked megathrusts. Here we analyze seismicity within a subducting oceanic slab, spanning ~50 major deep slow slip with tremor episodes over 17 years. Changes in rate, b-values, and stress orientations of in-slab seismicity are temporally associated with the episodes. Furthermore, although stress orientations in the slab below these slow slips may rotate slightly, in-slab orientations 20-50 km updip from there rotate farther, suggesting that previously-unrecognized transient slow slip occurs on the plate interface updip. We infer that fluid pressure propagates from slab to interface, promoting episodes of slow slip, which break mineral seals, allowing the pressure to propagate tens of km further updip along the interface where it promotes transient slow slips. The proposed methodology, based primarily on in-slab seismicity, may help monitor plate boundary conditions and slow slip phenomena, which can signal the beginning stages of megathrust earthquakes.

| S-EPMC8692312 | biostudies-literature

Deep Transient Slow Slip Detected by Survey GPS in the Region of Atacama, Chile.

Project description:We detected a long-term transient deformation signal between 2014 and 2016 in the Atacama region (Chile) using survey Global Positioning System (GPS) observations. Over an ?150 km along-strike region, survey GPS measurements in 2014 and 2016 deviate significantly from the interseismic trend estimated using previous observations. This deviation from steady state deformation is spatially coherent and reveals a horizontal westward diverging motion of several centimeters, along with a significant uplift. It is confirmed by continuous measurements of recently installed GPS stations. We discard instrumental, hydrological, oceanic, or atmospheric loading effects and show that the transient is likely due to deep slow slip in the transition zone of the subduction interface (?40- to 60-km depth). In addition, daily observations recorded by a continuous GPS station operating between 2002 and 2015 highlight similar transient signals in 2005 and 2009, suggesting a recurrent pattern.

| S-EPMC6472647 | biostudies-literature

Quartz c-axis fabric characterization of the strike-slip ductile deformation within the Three Pagodas shear zone, western Thailand.

Project description:The Three Pagodas shear zone is associated with mainland Southeast Asia deformations. The evolution of the shear zone is divided into deformation phases D1a, D1b, and D2. The first phase (D1a) involved ductile sinistral shearing associated with metamorphism. Foliations are well developed in a NW-SE with variable dips from east to west. Stretching lineations show NW-SE trending strike and flatly plunge to the south. Based on deformation patterns exhibited by outcrop and microscopic analysis, D1a shows NW-SE trending of ductile sinistral shearing. Additionally, the quantitative analysis of mylonitic quartzite exhibits an oblique angle of quartz grain shape fabric and quartz c-axis fabric asymmetry. Sinistral simple shear was confirmed by kinematic vorticity (Wk). The spatial distribution of the kinematic velocity number (Wk) of D1a shows a range between 0.93 and 0.99 at the central and western parts of the shear zone, which is higher than the 0.82-0.85 range for the eastern part of the shear zone. The strain variation within the Three Pagodas shear zone derived from the kinematic vorticity number (Wk) shows that the central and the western parts have been deformed under simple shear more than the eastern part. D1b is represented by the exhumation of high-grade metamorphic complex from sinistral transpression. The last stage (D2) involved the inversion of this strike-slip system, which is represented by dextral strike-slip faults.

| S-EPMC9732306 | biostudies-literature

Fluid flow shear stress over podocytes is increased in the solitary kidney.

Project description:BackgroundGlomerular hyperfiltration is emerging as the key risk factor for progression of chronic kidney disease (CKD). Podocytes are exposed to fluid flow shear stress (FFSS) caused by the flow of ultrafiltrate within Bowman's space. The mechanism of hyperfiltration-induced podocyte injury is not clear. We postulated that glomerular hyperfiltration in solitary kidney increases FFSS over podocytes.MethodsInfant Sprague-Dawley rats at 5 days of age and C57BL/6J 14-week-old adult mice underwent unilateral nephrectomy. Micropuncture and morphological studies were then performed on 20- and 60-day-old rats. FFSS over podocytes in uninephrectomized rats and mice was calculated using the recently published equation by Friedrich et al. which includes the variables-single nephron glomerular filtration rate (SNGFR), filtration fraction (f), glomerular tuft diameter (2RT) and width of Bowman's space (s).ResultsGlomerular hypertrophy was observed in uninephrectomized rats and mice. Uninephrectomized rats on Day 20 showed a 2.0-fold increase in SNGFR, 1.0-fold increase in 2RT and 2.1-fold increase in FFSS, and on Day 60 showed a 1.9-fold increase in SNGFR, 1.3-fold increase in 2RT and 1.5-fold increase in FFSS, at all values of modeled 's'. Similarly, uninephrectomized mice showed a 2- to 3-fold increase in FFSS at all values of modeled SNGFR.ConclusionsFFSS over podocytes is increased in solitary kidneys in both infant rats and adult mice. This increase is a consequence of increased SNGFR. We speculate that increased FFSS caused by reduced nephron number contributes to podocyte injury and promotes the progression of CKD.

| S-EPMC3888310 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data