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Stephen H. Kirby

Publications and source records attributed to Stephen H. Kirby.

At least 19 recordsLinked to original sources
USGS2023

Summary of the history and research of the U.S. Geological Survey gas hydrate properties laboratory in Menlo Park, California, active from 1993 to 2022

The U.S. Geological Survey (USGS) Clathrate Hydrate Properties Project, active from 1993 to 2022 in Menlo Park, California, stemmed from an earlier project on the properties of planetary ices supported by the National Aeronautics and Space Administration’s (NASA’s) Planetary Geology and Geophysics Program. We took a material science approach in both projects, emphasizing chemical purity of samples, having controlled grain size and grain texture, and having verified crystal structures and phase relations. A foundational contribution from our USGS Gas Hydrate Properties Laboratory (GHPL) was in demonstrating the ability to reproducibly create such pure clathrate hydrate samples for study. Clathrate sample synthesis was achieved by heating sieved and weighed pure granular water ice in the presence of cold clathrate-forming gas or liquid. During heating, the ice melts at the grain scale and reacts with the gas to form clathrate. The resulting material has the desired uniformity and purity, with known intergranular porosity; our subsequent measurements showed that these clathrates exhibited the established clathrate structures and phase relations. This novel synthesis method was successful in creating clathrates of pure methane, ethane, propane, carbon dioxide, and multi-component gases. By mixing sand or silt with granular ice, we were also able to make clathrate-sediment aggregates with controlled grain textures. This simple method, adopted by many others in the community, permitted us to measure the physical and chemical properties of well-characterized and well-crystallized clathrates and clathrate/sediment aggregates. At about the same time, we adapted conventional scanning electron microscopy to cryogenic conditions for analysis of grain-scale characteristics of clathrates made in the GHPL as well as those collected from nature by drill core. The uniformity and reproducibility of our samples also allowed us to investigate how clathrates respond to environmental changes in chemistry, temperature, and pressure: we measured chemical exchange rates with dissolved gas species—such as noble gases and chlorofluorocarbons—as well as rates of clathrate dissolution and decomposition. These advances include the first accurate mapping of the conditions that promote the remarkable process of “anomalous preservation” at room pressure, a metastability that offers potential application for low-cost and safe transportation of natural gas from gas fields far from pipelines. Another advancement stemming from the GHPL was the compaction of as-synthesized porous clathrates to nearly full density by applying external pressure using three different techniques. Compaction allows for high-accuracy measurements of many fundamental physical and chemical properties of these materials, such as elastic wavespeeds and moduli, complete thermal properties, decomposition rates, thermal expansion, and clathrate equations of state. These properties and others, in turn, have helped USGS scientists to interpret geophysical well logs and active geophysical surveys, as well as model the rates of gas production from hydrate deposits in nature. Studying this class of icy minerals that occur in abundance on Earth and in the outer solar system has been a fascinating laboratory journey. Here, we summarize the history and major findings of the USGS GHPL in Menlo Park, including both in-house research as well as findings from the synergistic collaborations with other agencies and institutes that were key to the success of our laboratory. The Menlo Park GHPL was more formally incorporated within the USGS Gas Hydrates Project, a collaboration among multiple USGS Science Centers, in the early 2000s under the leadership of Deborah Hutchinson, and now under the leadership of Carolyn Ruppel and Timothy Collett.

Open-File Report↗
USGS2015

Geological processes and orchid biogeography with applications to southeast central America

This contribution owes its origins to a paper presentation by Dr. Calloway H. Dodson at the Second International Conference on Neotropical Orchidology held in San José, Costa Rica in May of2003 (Dodson 2003). Dr. Dodson outlined some ofthe reasons to suspect that regional geological fac-tors may play important roles in orchid speciation and biogeography and gave examples from the northwestern South America. He also suggested that evolutionary change in orchid might occur over fairly short time periods, perhaps even as short as decades, centuries or millennia (Dodson 2003, SHK lecture notes). These ideas stimulated the author, a professional earth scientist, to begin thinking about how these exciting ideas could begin to be tested in Costa Rica neighboring and Central American countries, an area that has drawn him to return frequently over the last decade. The present contribution is a proposal for integrating geological observations, such as the chronology of arc volcanic activity in Nicaragua,Costa Rica, and Panama, in hypothesis forming and testing of the geographic distribution of orchids (and possibly other biota). I initially focus on comparisons between orchid inventories on the windward slopes of mountainous regions (elevation > 1000 m)with high rainfall (> 1-2 m) in tropical regions, the so-called tropical cloud forests. These regions represent the tropical pre-montane rain forestto lower montane tropical rain forest life zones of Holdridge(1967) and the montane vegetation zone applied to Costa Rica and Panama by Dressler (1993). An important message of this paper is that such tropical mountainous regions are not necessarily static, but may change in elevation over geologic time due to active tectonic deformation and uplift and that the presence of active volcanism in a mountain range may also introduce additional chemical factors, such as volcanic gases, acid rain, and volcanic soils, and also physical factors, such as interruption of gene flow by explosive eruptions and coverage by their air fall products such as ash (tephra), lava flows, and lahars (volcanic mudflows). Thus over a given geological time interval, forests may be slowly increasing in elevation by tectonic uplift or by the accumulation of volcanic products such as steep-sided strato volcanoes (built from both lavas and tephra), or by down-slope accumulations of lava flows or lahars. Mountains may also lose elevation by erosion or by tectonic subsidence. As we shall see, tropical Central America shows an extraordinarily high level of tectonic and volcanic history that has changed its geography and, by implication, climate, life zones,and likely orchid distribution. My working hypo thesis put forward for testing is that orchid adaptations to these changes may have led to the development of new species and endemism in this region.

Lankesteriana↗
USGS2014

A large mantle water source for the northern San Andreas Fault System: A ghost of subduction past

Recent research indicates that the shallow mantle of the Cascadia subduction margin under near-coastal Pacific Northwest U.S. is cold and partially serpentinized, storing large quantities of water in this wedge-shaped region. Such a wedge probably formed to the south in California during an earlier period of subduction. We show by numerical modeling that after subduction ceased with the creation of the San Andreas Fault System (SAFS), the mantle wedge warmed, slowly releasing its water over a period of more than 25 Ma by serpentine dehydration into the crust above. This deep, long-term water source could facilitate fault slip in San Andreas System at low shear stresses by raising pore pressures in a broad region above the wedge. Moreover, the location and breadth of the water release from this model gives insights into the position and breadth of the SAFS. Such a mantle source of water also likely plays a role in the occurrence of Non-Volcanic Tremor (NVT) that has been reported along the SAFS in central California. This process of water release from mantle depths could also mobilize mantle serpentinite from the wedge above the dehydration front, permitting upward emplacement of serpentinite bodies by faulting or by diapiric ascent. Specimens of serpentinite collected from tectonically emplaced serpentinite blocks along the SAFS show mineralogical and structural evidence of high fluid pressures during ascent from depth. Serpentinite dehydration may also lead to tectonic mobility along other plate boundaries that succeed subduction, such as other continental transforms, collision zones, or along present-day subduction zones where spreading centers are subducting.

California↗
USGS2013

The SAFRR Tsunami Scenario

The U.S. Geological Survey and several partners operate a program called Science Application for Risk Reduction (SAFRR) that produces (among other things) emergency planning scenarios for natural disasters. The scenarios show how science can be used to enhance community resiliency. The SAFRR Tsunami Scenario describes potential impacts of a hypothetical, but realistic, tsunami affecting California (as well as the west coast of the United States, Alaska, and Hawaii) for the purpose of informing planning and mitigation decisions by a variety of stakeholders. The scenario begins with an Mw 9.1 earthquake off the Alaska Peninsula. With Pacific basin-wide modeling, we estimate up to 5m waves and 10 m/sec currents would strike California 5 hours later. In marinas and harbors, 13,000 small boats are damaged or sunk (1 in 3) at a cost of $350 million, causing navigation and environmental problems. Damage in the Ports of Los Angeles and Long Beach amount to $110 million, half of it water damage to vehicles and containerized cargo. Flooding of coastal communities affects 1800 city blocks, resulting in $640 million in damage. The tsunami damages 12 bridge abutments and 16 lane-miles of coastal roadway, costing $85 million to repair. Fire and business interruption losses will substantially add to direct losses. Flooding affects 170,000 residents and workers. A wide range of environmental impacts could occur. An extensive public education and outreach program is underway, as well as an evaluation of the overall effort.

Conference Paper↗
USGS2013

U.S. Geological Survey natural hazards science strategy— Promoting the safety, security, and economic well-being of the Nation

Executive Summary The mission of the U.S. Geological Survey (USGS) in natural hazards is to develop and apply hazard science to help protect the safety, security, and economic well-being of the Nation. The costs and consequences of natural hazards can be enormous, and each year more people and infrastructure are at risk. USGS scientific research—founded on detailed observations and improved understanding of the responsible physical processes—can help to understand and reduce natural hazard risks and to make and effectively communicate reliable statements about hazard characteristics, such as frequency, magnitude, extent, onset, consequences, and where possible, the time of future events. To accomplish its broad hazard mission, the USGS maintains an expert workforce of scientists and technicians in the earth sciences, hydrology, biology, geography, social and behavioral sciences, and other fields, and engages cooperatively with numerous agencies, research institutions, and organizations in the public and private sectors, across the Nation and around the world. The scientific expertise required to accomplish the USGS mission in natural hazards includes a wide range of disciplines that this report refers to, in aggregate, as hazard science. In October 2010, the Natural Hazards Science Strategy Planning Team (H–SSPT) was charged with developing a long-term (10-year) Science Strategy for the USGS mission in natural hazards. This report fulfills that charge, with a document hereinafter referred to as the Strategy, to provide scientific observations, analyses, and research that are critical for the Nation to become more resilient to natural hazards. Science provides the information that decisionmakers need to determine whether risk management activities are worthwhile. Moreover, as the agency with the perspective of geologic time, the USGS is uniquely positioned to extend the collective experience of society to prepare for events outside current memory. The USGS has critical statutory and nonstatutory roles regarding floods, earthquakes, tsunamis, landslides, coastal erosion, volcanic eruptions, wildfires, and magnetic storms—the hazards considered in this plan. There are numerous other hazards of societal importance that are considered either only peripherally or not at all in this Strategy because they are either in another of the USGS strategic science plans (such as drought) or not in the overall mission of the USGS (such as tornados).

Circular↗
USGS2013

Intermediate‐depth intraslab earthquakes and arc volcanism as physical expressions of crustal and uppermost mantle metamorphism in subducting slabs

We elaborate on the well-known spatial association between axc volcanoes and Wadati Benioff zones and explore in detail their genetic relationships as dual physical expressions of slab metamorphism of the oceanic crust and uppermost mantle. At hypocentral depths less than 200 km intra slab Wadati-Benioff earthquakes tend to occur near the top surfaces of slabs. Subduction of very young lithosphere (age < 15-25 Ma) with high heat flow (> 75 mW/m 2) produces mainly shallow earthquakes and spaxse or absent arc volcanism. Subduction of older crust with normal heat flow (50-65 mW/m 2) produces markedly deeper intraslab earthquakes and generally normal volcanic vigor. Seismological observations show that the low-seismic-velocity gabbroic mineralogy of the crust may persist to depths of as much as 150 km in old, cold lithosphere but only to depths of 50-60 km in young, warm slabs. Metamorphic processes in the crust and shallow upper mantle of subducting slabs and the reactivation of faults originally created at shallow depths in the ocean basins probably control the occurrence of intraslab earthquakes to depths of as much as 350 kin. A conceptual model for this metamorphism incorporates the likely effects of water liberated by dehydration. Such dehydration facilitates both brittle faulting by fault reactivation and promotes the kinetics of the transformation of the anhydrous gabbro component of the crust to eclogite. Finite-element modelling shows that densification to eclogite is expected to produce extensional stresses in transformed crust and a smaller compression in the underlying mantle. This model helps explain why most intermediate-depth intraslab earthquakes occur just below the top surfaces of slabs and why many have focal mechanisms indicating down-dip extension. Young, warm slabs have mostly shallow intraslab earthquakes and sparse axc volcanoes because dehydration and eclogite formation largely cease before such slabs axe in contact with asthenosphere. These processes are evidently delayed by kinetic hindrance and the high pressure stability of hydrous phazes at low temperatures in older, colder subducting crust, and thus earthquake activity and asthenospheric-wedge melting tend to be focused at depths of 100-170 kin. Anomalous behavior correlated with the subduction of island-and seamount chains appears to be associated with anomalou shallow intraplate faulting and with perturbations of slab metamorphism by these chains.

Geophysical Monograph↗
USGS2013

Intermediate-depth earthquakes facilitated by eclogitization-related stresses

Eclogitization of the basaltic and gabbroic layer in the oceanic crust involves a volume reduction of 10%–15%. One consequence of the negative volume change is the formation of a paired stress field as a result of strain compatibility across the reaction front. Here we use waveform analysis of a tiny seismic cluster in the lower crust of the downgoing Pacific plate and reveal new evidence in favor of this mechanism: tensional earthquakes lying 1 km above compressional earthquakes, and earthquakes with highly similar waveforms lying on well-defined planes with complementary rupture areas. The tensional stress is interpreted to be caused by the dimensional mismatch between crust transformed to eclogite and underlying untransformed crust, and the earthquakes are probably facilitated by reactivation of fossil faults extant in the subducting plate. These observations provide seismic evidence for the role of volume change–related stresses and, possibly, fluid-related embrittlement as viable processes for nucleating earthquakes in downgoing oceanic lithosphere.

Geology↗
USGS2013

The SAFRR tsunami scenario: Improving resilience for California

On March 11, 2011, the Tohoku earthquake and the resulting tsunami devastated Japan with a disaster of unfathomable proportions. Five thousand miles away, the waves from Tohoku caused $50 to 100 million in damages in California. Although this pales in comparison to the loss of lives and property in Japan, the U.S. Government must ask whether California, and the national economy, will someday face worse consequences from other distant-source tsunamis. Unfortunately, the answer is “yes.”

California↗
USGS2013

SAFRR (Science Application for Risk Reduction) Tsunami Scenario--Executive Summary and Introduction: Chapter A in The SAFRR (Science Application for Risk Reduction) Tsunami Scenario

The Science Application for Risk Reduction (SAFRR) tsunami scenario depicts a hypothetical but plausible tsunami created by an earthquake offshore from the Alaska Peninsula and its impacts on the California coast. The tsunami scenario is a collaboration between the U.S. Geological Survey (USGS), the California Geological Survey, the California Governor’s Office of Emergency Services (Cal OES), the National Oceanic and Atmospheric Administration (NOAA), other Federal, State, County, and local agencies, private companies, and academic and other institutions. This document presents evidence for past tsunamis, the scientific basis for the source, likely inundation areas, current velocities in key ports and harbors, physical damage and repair costs, economic consequences, environmental and ecological impacts, social vulnerability, emergency management and evacuation challenges, and policy implications for California associated with this hypothetical tsunami. We also discuss ongoing mitigation efforts by the State of California and new communication products. The intended users are those who need to make mitigation decisions before future tsunamis, and those who will need to make rapid decisions during tsunami events. The results of the tsunami scenario will help managers understand the context and consequences of their decisions and how they may improve preparedness and response. An evaluation component will assess the effectiveness of the scenario process for target stakeholders in a separate report to improve similar efforts in the future.

California↗
USGS2012

Probing the Earth's strength: Can we measure small stress at high pressure?

Simulating the conditions and processes that occur in the Earth's deep interior has been a major goal of experimental geophysics since the 1920s. In particular, pioneers such as P. W. Bridgman, David Griggs, Hugh Heard, Mervyn Paterson, William Brace, and their colleagues sought to establish the basic relations between differential stresses and rock and mineral deformation under pressure-temperature conditions that favor such inelastic processes as brittle fracture, frictional sliding, plastic deformation, and dynamic metamorphism. This work has been applied to diverse problems in the Earth sciences, including the physical nature of earth quake sources, the forces that drive and resist plate movement, deformation under partial-melting conditions at the tops of mantle plumes, the flexure of the lithosphere, post-glacial rebound, and the origin of the preferred orientation of minerals and the resultant seismic anisotropy and metamorphic textures.

Eos, Transactions, American Geophysical Union↗
USGS2012

The 9 June 94 Bolivian Deep Earthquake: An exceptional event in an extraordinary subduction zone

We investigate the physical setting of the Bolivian shock based on the history of the subducting Nazca plate, intraslab seismicity, deep seismic moment release, and seismic tomography. South America has two broad regions of reverse arc curvature. Subduction constrained to this unique geometry produces slab kinking contortions that may cause unusual slab thickening as they sink to the bottom of the transition zone and encounter resistance to penetration into the lower mantle. Such contortions are observed at intermediate depths “upstream” from the slab source regions of both the great 1970 Colombian and 1994 Bolivian events. Thickening helps explain how the Nazca slab accommodates large seismic source dimensions at depths of 625–650 km.

Geophysical Research Letters↗
USGS2012

The effects of the α‐β phase transformation on the creep properties of hydrolytically‐weakened synthetic quartz

Nine rectangular prisms of hydro‐thermally‐grown synthetic quartz crystals with 900 atomic ppm H + were loaded in compression at 1400 bars stress and temperatures between 403 and 764°C. The a and c directions were at 45° to the compression direction, and the slip system appears to operate over the entire range of temperatures. The strain vs. time curves were sigmoidal in shape; an incubation stage of accelerating creep rates was followed by a hardening stage in which creep rates decreased with time. The creep rate (⋵) vs. temperature (T) data were found to fit very well an Arrehenius law of the form where E* is the activation energy for creep. E* is 38.9 ± 2.1 kcal/mole in the α field and 14.3 ± 4.7 kcal/mole in the β field. An offset in the maximum strain rates occurs at the transition temperature, with the β phase creeping at less than half the rate of the α phase. It is suggested that the changes in creep parameters are due to the effects of the inversion on the rates of oxygen diffusion associated with the dissolved water, which hydrolytically weakens the crystals. The α‐β transformation involves rather subtle structural changes. No bond breaking occurs and the change in density is rather small. The transformations responsible for the transition zone of the mantle are reconstructive (involving extensive bond breaking and complete atomic reorganization) and the density changes are large. Thus the potential for large effects of these transformations on creep properties is even greater.

Geophysical Research Letters↗
USGS2012

Experimental deformation of polycrystalline H2O ice at high pressure and low temperature: Preliminary results

Interest in the mechanical properties of water ice under the conditions in which it exists in the outer solar system has motivated the development and use of a new high‐pressure, low‐temperature triaxial deformation apparatus. Constant displacement rate tests on 70 samples of pure polycrystalline water ice have been performed at temperatures 77≤≤258 K, confining pressures 0.1≤≤350 MPa, and strain rates 3.5×10≤ ≤3.5×10 s. In most cases, the ice polymorph tested was ice . Both brittle and ductile behavior have been observed. Brittle behavior of ice, promoted by lower pressure, lower temperature, and higher strain rate, is analogous to that in rocks, with the important exception that brittle fracture strength becomes independent of confining pressure above 50 MPa pressure and the fracture angle is approximately 45° to the loading direction (i.e., the coefficient of internal friction is approximately zero). Ductile flow, the predominant behavior in our tests at ≥195 K, follows a law of form = σ exp (−*/) (σ is stress; is the gas constant; , * are material constants). Three sets of material constants are required to fit the data, with changes in sets (or mechanisms) occurring near 243 K and 195 K. The value of remains near 4 throughout the measured ductile field, but * drops from 91 to 61 to 31 /mole as temperature decreases. The maximum brittle strength measured was 171 MPa; the maximum ductile strength measured was 91 MPa. At confining pressures near the phase transition pressure of ice → ice II, the ductile strength is observed to drop dramatically. Some overlap with previous work occurs at higher temperatures and lower pressures. Agreement with present work is generally good, both quantitatively in the values of and *, and qualitatively in the mechanism of deformation. Although the ductile strengths measured here are somewhat higher than expected on the basis of extrapolations of previous work, the low value of * at <195 K indicates that the ice layer on icy bodies in the solar system is much weaker than has generally been predicted.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Introduction and digest to the Special Issue on Chemical Effects of Water on the Deformation and Strengths of Rocks

The important role of pore pressure in promoting such brittle processes as cataclasis, hydraulic fracturing, large‐scale faulting, and earthquakes within the crust is widely accepted in geology and geophysics [, 1957; , 1959; , 1958; ., 1963; , 1968; ., 1968; ., 1976; , 1973, 1980; , 1981]. Provided that fluid pressure is fully communicated with rock pore space, the effective normal stresses that control crack growth, macroscopic fracture, and friction are reduced by the magnitude of the fluid pressui'e. Beyond this physical effect of pore fluids, there are chemical effects of water on the strength of rocks that are also important in governing differential stresseg and flow in the continental crust. Some of these chemical effects of water on rock deformation have long been recognized.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Experimental deformation of topaz crystals: Possible embrittlement by intracrystalline water

Crystallographically oriented single‐crystal prisms of gem quality topaz (composition AlSiO (OH− F) where x = 0.04 ± 0.01) were deformed at a confining pressure of 1.50 GPa, a temperature of 800°C, and a strain rate of 2×10 s. Under nearly identical conditions, all crystals of anhydrous rock‐forming minerals that have been tested to date, such as olivine, quartz, feldspars, pyroxenes, and refractory oxides, deform plastically; in contrast, our topaz crystals failed by brittle fracture regardless of the orientation of the compression direction. No optical evidence for plastic deformation was detected. Another suite of experiments with compression perpendicular to the (001) cleavage at = 100°–950°C and a strain rate of 2×10 s displayed two regimes of behavior: (1) at >400°C, fracture strength was independent of temperature, and fracture occurred on one or two surfaces parallel to {103}; (2) at <400°C, the fracture strength increased rapidly with decreasing temperature, no macroscopic stress drop was observed, and many closely spaced conjugate fractures formed on (103) and (103). The anomalous brittleness of topaz compared to anhydrous silicate and oxide crystals indicates that intracrystalline “water” plays a role in the embrittlement. We suggest that water within the topaz crystals promotes fracture in ways similar to the mechanisms of slow crack growth aided by environmental moisture.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Effects of compression direction on the plasticity and rheology of hydrolytically weakened synthetic quartz crystals at atmospheric pressure

A hydrothermally grown synthetic quartz crystal with 370±60 ppm hydroxyl impurity was cut into right rectangular prisms in eight crystallographic orientations. We compressed the prisms under constant axial force corresponding to a uniaxial stress of 140.0±0.5 MPa, and temperatures of 510° and 750°C. All but one of the samples sustained permanent axial strains of 2–3%. We established the operating slip systems from specimen shape change, slip bands and dislocation etch pits on polished surfaces, crystallographic orientation changes, stress optical features in thin sections, and transmission electron microscopy. The observed creep behavior and plasticity divided the samples into three groups: (1) Crystals compressed at 45° to [0001] and [ ] and those compressed ⊥( ) and ⊥( ) deformed principally by slip parallel to [0001]. Creep rates were relatively high and were not strongly sensitive to test temperature. Dislocation arrays approximately parallel to ( ) are common. Dislocation loops are elongate parallel to [0001], indicating that the edge segments were more mobile than the screw segments. (2) The second group of samples were loaded normal to [0001] in three orientations: ⊥( ), ⊥( ), and at 45° to ( ). These samples deformed primarily by { } 〈a〉 slip with some evidence for secondary slip on the other systems. They were more creep resistant than the first group and displayed a much higher sensitivity of creep rate to test temperature. Dislocation loops are very elongate parallel to [0001], indicating that the screw dislocation segments were much more mobile than the edge segments. (3) A sample compressed parallel to [0001] at 750°C crept at a barely detectable rate (∼10 s) and no optical scale slip features were observed. These results confirm our earlier work on one orientation each from groups 1 and 2, which indicated a strong creep anisotropy for this same crystal. This creep anisotropy parallels a remarkably similar anisotropy in the diffusivity of impurities in quartz, suggesting a causal relationship between impurity diffusion and creep associated with hydrolytic weakening. Appendix Tables A1‐A5 are available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009. Document B84‐004; $2.50. Payment must accompany order.

Journal of Geophysical Research B: Solid Earth↗