A finite difference method for earthquake sequences in poroelastic solids     

Kim Torberntsson  Vidar Stiernström  Ken Mattsson  Eric M. Dunham 《Computational Geosciences》2018,22(5):1351-1370

Induced seismicity (earthquakes caused by injection or extraction of fluids in Earth’s subsurface) is a major, new hazard in the USA, the Netherlands, and other countries, with vast economic consequences if not properly managed. Addressing this problem requires development of predictive simulations of how fluid-saturated solids containing frictional faults respond to fluid injection/extraction. Here, we present a finite difference method for 2D linear poroelasticity with rate-and-state friction faults, accounting for spatially variable properties. Semi-discrete stability and accuracy are proven using the summation-by-parts, simultaneous-approximation-term (SBP-SAT) framework for discretization and boundary condition enforcement. Convergence rates are verified using the method of manufactured solutions and comparison to the analytical solution to Mandel’s problem. The method is then applied to study fault slip triggered by fluid injection and diffusion through high-permeability fault damage zones. We demonstrate that in response to the same, gradual forcing, fault slip can occur in either an unstable manner, as short-duration earthquakes that radiate seismic waves, or as stable, aseismic, slow slip that accumulates over much longer time scales. Finally, we use these simulation results to discuss the role of frictional and elastic properties in determining the stability and nature of slip.  相似文献   

The age of Earth’s largest volcano: Tamu Massif on Shatsky Rise (northwest Pacific Ocean)   总被引：1，自引：0，他引：1  

Jörg Geldmacher  Paul van den Bogaard  Ken Heydolph  Kaj Hoernle 《International Journal of Earth Sciences》2014,103(8):2351-2357

This study presents laser step-heating ⁴⁰Ar/³⁹Ar age determinations of basaltic lava samples from Tamu Massif, the oldest and largest edifice of the submarine Shatsky Rise in the northwest Pacific and Earth’s proposed largest volcano. The rocks were recovered during Integrated Ocean Drilling Program Expedition 324, which cored 160 m into the igneous basement near the summit of Tamu Massif. The analyzed lavas cover all three major stratigraphic groups penetrated at this site and confirm a Late Jurassic/Early Cretaceous age for the onset of Shatsky Rise volcanism. Lavas analyzed from the lower and middle section of the hole yield plateau ages between 144.4 ± 1.0 and 143.1 ± 3.3 Ma with overlapping analytical errors (2σ), whereas a sample from the uppermost lava group produced a significantly younger age of 133.9 ± 2.3 Ma suggesting a late or rejuvenated phase of volcanism. The new geochronological data infer minimum (average) melt production rates of 0.63–0.84 km³/a over a time interval of 3–4 million years consistent with the presence of a mantle plume.  相似文献   

Distribution of nitrous oxide dissolved in water masses in the eastern subtropical North Pacific and its origin inferred from isotopomer analysis     

Ayako Fujii  Sakae Toyoda  Osamu Yoshida  Shuichi Watanabe  Ken’ichi Sasaki  Naohiro Yoshida 《Journal of Oceanography》2013,69(2):147-157

N₂O concentration and its isotopomer ratios were measured over a wide area from San Diego to Honolulu in the eastern subtropical North Pacific (ESNP). Waters in the study area had an N₂O maximum (38.2–50.5 nmol kg^?1) at 600–1000 m depth, which is similar to the profiles obtained previously in other areas in the North Pacific. We separated the seawater into five water masses (two for the surface layer, two for the middle layer, and one for the deep layer) and deduced N₂O production–consumption mechanisms in each water body by use of N₂O isotopomer ratios. The results showed that the mechanisms differ slightly among water masses. In the “coastal” surface layer, N₂O is produced by nitrification (NH₂OH oxidation). In the “open ocean” surface layer, it is produced mainly by nitrifier denitrification and to a lesser extent by nitrification under substrate-limited conditions. In both “upwelling” and “open ocean” middle layers it is produced mainly by denitrification and to a lesser extent by nitrifier denitrification. It is also partly reduced. In the deep layer, it is produced predominantly by denitrification with partial reduction. In this way, isotopomers aid elucidation of production–consumption mechanisms of N₂O in the sea even though the mechanisms cannot always be ascertained.  相似文献   

Rapid shipboard identification and enumeration of pelagic marine fish eggs by a simple photographic technique (note)     

Robin C. Murdoch  Richard J. Singleton  Ken R. Grange 《新西兰海洋与淡水研究杂志》2013,47(1):137-140

A technique is described for obtaining rapid high‐quality silhouette photographs of plankton samples at sea. This technique was designed to facilitate identification and enumeration of pelagic marine fish eggs in near real‐time. It uses readily available photographic materials and unlike previously described techniques, the silhouettes are recorded directly on to photographic paper rather than film. The resolution is adequate for microscopic measurements. Examples are presented from a cruise off Westland, New Zealand, which investigated the distribution of hoki eggs.  相似文献   

BIOB: A mathematical model for the biodegradation of low solubility hydrocarbons     

Xiaolong Geng  Michel C. Boufadel  Yves R. Personna  Ken Lee  David Tsao  Erik D. Demicco 《Marine pollution bulletin》2014

Modeling oil biodegradation is an important step in predicting the long term fate of oil on beaches. Unfortunately, existing models do not account mechanistically for environmental factors, such as pore water nutrient concentration, affecting oil biodegradation, rather in an empirical way. We present herein a numerical model, BIOB, to simulate the biodegradation of insoluble attached hydrocarbon. The model was used to simulate an experimental oil spill on a sand beach. The biodegradation kinetic parameters were estimated by fitting the model to the experimental data of alkanes and aromatics. It was found that parameter values are comparable to their counterparts for the biodegradation of dissolved organic matter. The biodegradation of aromatics was highly affected by the decay of aromatic biomass, probably due to its low growth rate. Numerical simulations revealed that the biodegradation rate increases by 3–4 folds when the nutrient concentration is increased from 0.2 to 2.0 mg N/L.  相似文献   

Growing season expansion and related changes in monthly temperature and growing degree days in the Inter-Montane Desert of the San Luis Valley, Colorado     

Ken Mix  Vicente L. Lopes  Walter Rast 《Climatic change》2012,114(3-4):723-744

Most climate change studies on high elevation ecosystems identify changes in biota, while several report abiotic factors. However, very few report expansion of the freeze-free period, or discuss monthly changes of temperature and growing degree days (GDD) during the growing season. This study provides initial data on agriculturally-related aspects of climate change during the growing season (M-J-J-A-S) in the inter-montane desert of the San Luis Valley (SLV), Colorado. Temperature data were gathered from 7 climate stations within the SLV. Based on ordinal days, the last vernal freeze is occurring (p?<?0.05) earlier at 3 stations than in prior years, ranging between 5.52 and 11.86?days during 1981–2007. Significantly-later autumnal freezes are occurring at 5 stations by 5.95–18.10?days, while expansion of the freeze-free period was significantly longer at all stations by 7.20–24.21?days. The freeze-free period averaged about 93?days prior to the 1980s, but now averages about 107?days. Increases (p?<?0.05) in daily mean, maximum, minimum temperature occurred at nearly all stations for each month. Increases in GDD₁₀, GDD_4.4 (potato) and GDD_5.5 (alfalfa) also occurred at nearly all stations for all months during 1994–2007. Higher temperatures increase the number of GDD, quickening crop growth and maturity, and potentially reducing yield and quality unless varieties are adapted to changes and water is available for the season extension and increased evapotranspiration.  相似文献   

A Motion-Stabilized W-Band Radar for Shipboard Observations of Marine Boundary-Layer Clouds     

Ken Moran  Sergio Pezoa  Chris Fairall  Chris Williams  Tom Ayers  Alan Brewer  Simon P. de Szoeke  Virendra Ghate 《Boundary-Layer Meteorology》2012,143(1):3-24

Cloud radars at X, Ka and W-bands have been used in the past for ocean studies of clouds, but the lack of suitable stabilization has limited their usefulness in obtaining accurate measurements of the velocity structure of cloud particles and the heights of cloud features. A 94 GHz (W-band) radar suitable for use on shipboard studies of clouds has been developed that is small and lightweight and can maintain the radar’s beam pointing in the vertical to reduce the affects of the pitch and roll of the ship. A vertical velocity sensor on the platform allows the effects of the ship’s heave to be removed from the measured cloud particle motions. Results from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-Rex) field program on the NOAA vessel Ronald H. Brown demonstrate the improvements to the cloud measurements after the ship’s motion effects are removed. The compact design of the radar also makes it suitable for use in aircraft studies. The radar is being repackaged to fit in an aft bay of a NOAA P3 aircraft to observe sea-spray profiles during ocean storms.  相似文献   

Characterization of locally available soil as a liner material for solid waste landfills in Sri Lanka     

Hafiz Muhammad Awais Rashid  J. A. D. K. Wanigarathna  L. C. Kurukulasuriya  N. H. Priyankara  A. M. N. Alagiyawanna  Takeshi Saito  Ken Kawamoto 《Environmental Earth Sciences》2017,76(11):396

This study aimed to develop a low-cost and effective clay liner material for solid waste landfills in Sri Lanka. A locally available clayey soil and its admixtures with 5 and 10% bentonite were examined for this purpose. Laboratory experiments to determine soil plasticity and swell index were carried out on the tested samples. Hydraulic conductivity (k) tests were carried out in the laboratory using water and an aqueous solution of CaCl₂ on unconsolidated samples prepared by either dry or slurry packing and pre-consolidated samples with five different consolidation pressures (p) from 10 to 200 kPa. Measured liquid limits for tested admixtures increased with increasing bentonite contents and correlated well with measured values of the swell index. The difference in permeant solutions had little effect on measured k values for both unconsolidated and pre-consolidated samples. The hydraulic conductivities were highly affected by changing p, i.e., the k values decreased on two orders of magnitude as p increased from 10 to 200 kPa. The Kozeny–Carman equation, a theoretical permeability model that expresses the k-porosity relationship, was applied to measured data including reported values. Results showed the Kozeny–Carman equation captured well the porosity-dependent k values for tested soils and their admixtures with bentonite under a wide range of void ratios, suggesting that the Kozeny–Carman equation is a useful tool to estimate the magnitude of k values for differently compacted soil and its bentonite admixtures.  相似文献   

纯化油田湖相滩坝薄储层含油性差异及控制因素          下载免费PDF全文

郭晓  巨恳  戴越  袁青春 《山东国土资源》2017,33(10)

纯化油田滩坝储层岩性复杂,泥岩、砂岩和碳酸盐岩呈薄层状频繁互层,不同储层的物性差异明显。综合运用岩心、测井、扫描电镜、物性实验和生产动态等资料,对储层含油性差异及控制因素进行了研究。结果表明:研究区发育坝、砂质滩、颗粒滩、泥晶滩及浅湖泥5种微相,物源、成岩作用、沉积微相和储层厚度均对储层含油性有控制作用。优质储层在垂向上有分层性,纯上砂层组砂岩储层优于纯下砂层组碳酸盐岩储层,其中成岩作用改造作用明显,钙质胶结使砂岩物性变差,溶蚀作用使鲕粒灰岩孔渗性优于泥晶灰岩;平面上有分区性,与沉积微相密切相关,坝、砂质滩最好,颗粒滩次之,泥晶滩最差;同一相带内又受储层厚度影响,厚度越大产油越好。  相似文献   

Atmospheric methane over the past 2000 years from a sub-tropical ice core,central Himalayas     

Ken MacClune 《山地科学学报》2010,7(1):1-14

A high-resolution 2000-year methane record has been constructed from an ice core recovered at 7200 m a.s.l. on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval 0-1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in pre- industrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship between atmospheric methane and climate change.  相似文献