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New Zealand’s Alpine Fault (AF) ruptures quasi-periodically in large-magnitude earthquakes. Paleoseismological evidence suggests that about half of all recognized AF earthquakes terminated at the boundary between the Central and South Westland sections of the fault. There, fault geometry and the polarity of uplift change. The South Westland AF exhibits oblique-normal fault motion on a structure oriented 055/82SE that, for at least 35 km along strike, contains saponite-rich principal slip zone gouges. New hydrothermal friction experiments reveal that the saponite fault gouge is frictionally weak, exhibiting friction coefficients between =0.12 and =0.16 for a range of temperatures (T=25–210 C) and effective normal...
We present whole-rock geochemical analyses of 12 core samples obtained from three serpentinite mud volcanoes (Yinazao, Asut Tesoru, and Fantangisna) located on the forearc of the Mariana subduction system, where the Pacific Plate descends beneath the Philippine Sea Plate. The core was collected during International Ocean Discovery Program Expedition 366 of 2016-2017. The materials comprising the mud volcanoes have risen diapirically along normal faults in the forearc that may extend down to the subducting slab. Ten of the samples are thoroughly serpentinized ultramafic rocks. The other two come from cored intervals into Fantangisna mud volcano that contain materials derived from the subducting Pacific Plate, and...
Categories: Data;
Tags: Geochemistry,
Mariana Trench,
Micronesia,
Northern Mariana Islands,
Structural Geology,
Laboratory slide-hold-slide tests, combined with flow through tests, conducted on Westerly granite with 30 degree sawcut. Tests were conducted with a constant confining pressure of 30 MPa with an average pore pressure of 10 MPa at temperatures of 23 and 200 degC. Three fluid flow conditions were examined (1) no flow, (2) cycled flow, and (3) continuous flow.
Earthquake instability occurs as a result of strength loss during sliding on a fault. It has been known for over 50 years that fault compaction or dilatancy may cause significant weakening or strengthening by dramatically changing the fluid pressure trapped in faults. Despite this fundamental importance, we have no real understanding of the exact conditions that lead to compaction or dilation during nucleation or rupture. To date, no direct measurements of pore pressure changes during slip in hydraulically isolated faults have been reported. We show direct examples of fluid pressure variations during nucleation and rupture using a miniature pressure transducer embedded in an experimental fault. We demonstrate that...
Enhanced reservoir connectivity generally requires maximizing the intersection between hydraulic fracture (HF) and preexisting underground natural fractures (NF), while having the hydraulic fracture continue to propagate across the natural fractures. Observations of downhole core samples suggest that these natural fractures are in fact veins filled with minerals such as calcite (Mighani et al., 2016). We study this interaction during the approach of a hydraulic fracture to a smooth saw-cut fracture under triaxial stress conditions. The specimen is Solnhofen limestone, a fine-grained (<5 µm grain), low permeability (<10 nD) carbonate. The differential stress (1-20 MPa) and inclination of the fault which determines...
Data are time series of clay shearing tests presented in 'Friction in clay-bearing faults increases with the ionic radius of interlayer cations' by Sakuma et al. in Communications Earth & Environment, 2022. Data were used for Figure 1 and Supplementary Figure 8 in that paper. Files contain shear strength as a function of fault slip in laboratory tests for brine-saturated montmorillonite clay.
Electrical resistivity measurements of Alpine Fault, NZ outcrop samples saturated with 0.1 M KCl brine and tested at confining pressure of 5 to 200 MP at room temperature.
This data release comprises three separate datasets and their accompanying metadata, in zip files. The data were acquired as part of a laboratory study of the response of ultramafic materials to shear at hydrothermal conditions. The principal dataset consists of the strength-displacement data from 28 friction experiments acquired on gouges prepared from peridotite rock samples and from separates of its principal mineral constituents olivine and orthopyroxene. The other two datasets present mineralogical data for the run products obtained by X-ray diffraction (XRD) and energy dispersive system (EDS) techniques.
Six time-series data files are included in this release. The files contain mechanical data (described in metadata file below) collected during deformation experiments performed on obsidian gouge. A detailed description of the experiments along with the data reduction procedures are provided in the published manuscript: Proctor, B.P., Lockner, D.A., Lowenstern, J.B., and Beeler, N.M., 2017, Conversion of Wet Glass to Melt at Lower Seismogenic Zone Conditions: Implications for Pseudotachylyte Creep: Geophysical Research Letters, v. 44, no. 20, p. 10248–10255, https://doi.org/10.1002/2017GL075344.
Core samples from the International Ocean Discovery Program (IODP) Expedition 366 were tested in the laboratory to determine permeability, porosity, density, and frictional strength and their relation to mineralogy as part of an effort to understand hydro-mechanical processes at convergent plate margins. Seven samples were tested from a depth range of 19.6 to 197.9 m below the sea floor. The samples were derived from three serpentinite mud volcanoes in the Mariana forearc region, formed where slab-derived fluids and materials ascend along faults. The physical characteristics mirror compositional differences between predominantly serpentine-rich and saponite-rich samples. Permeability values ranged from 10-17 to...
Categories: Data;
Tags: Geophysics,
Marine Geology,
USGS Science Data Catalog (SDC),
marine geology,
oceans
Recent widespread seismicity in Oklahoma is attributed to the reactivation of pre existing, critically-stressed, and seismically unstable faults due to decades of wastewater injection. However, the structure and properties of the reactivated faults remain concealed by the sedimentary cover. Here, we explore the major ingredients needed to induce earthquakes in Oklahoma by characterizing basement faults in the field, in seismic surveys and via rock mechanics experiments. Outcrop and satellite mapping reveal widespread fracture/fault systems with trends that display a marked similarity to the trends of recent earthquake lineaments. Our 3D seismic analyses show steeply-dipping basement-rooted faults that penetrate...
Categories: Data;
Tags: Seismology,
USGS Science Data Catalog (SDC),
geoscientificInformation,
seismology
The data are time series of laboratory strength and permeability measurements of 5 rock types. The tests were conducted as part of an interlaboratory comparison to determine repeatability of measurements using different test equipment and measurement techniques. These data represent the USGS contribution to the study. Other contributing organizations are archiving data sets separately.
Abstract: Enhanced reservoir connectivity generally requires maximizing the intersection between hydraulic fracture (HF) and preexisting underground natural fractures (NF), while having the hydraulic fracture cross the natural fractures (and not arrest). We have studied the interaction between a hydraulic fracture and a polished saw-cut fault. The experiments include a hydraulic fracture initiating from a pressurized axial borehole (using water) that approaches a dry fault that is inclined at an angle θ with respect to the borehole axis. The experiments are conducted on Poly(methyl) Meta Acrylate (PMMA) and Solnhofen limestone, a finely grained (<5 μm grain), low permeability (<10 nD) carbonate. The confining pressure...
Laboratory slide-hold-slide tests were conducted in a conventional triaxial deformation configuration on 1-inch diameter cylindrical cores of Westerly granite bisected by a sawcut oriented at 30 degrees from vertical. Tests were conducted at a constant confining pressure of 30 MPa with a 10 MPa pore fluid pressure. The pore fluid was deionized water. Experiments were conducted at temperatures of 22, 100, 200, and 250 degC.
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