Research Geophysicist
Email:
dlockner@usgs.gov
Office Phone:
650-329-4826
Fax:
650-329-5163
ORCID:
0000-0001-8630-6833
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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...
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Geophysics,
New Zealand,
Structural Geology,
USGS Science Data Catalog (SDC),
earthquake hazard, All tags...
frictional strength,
stress state, Fewer tags
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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, All tags...
USGS Science Data Catalog (SDC),
geochemistry,
mud volcano,
serpentinite,
subduction zone, Fewer tags
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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.
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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...
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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...
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