Bayesian and Neural Network Approaches to Estimate Deep Temperature Distribution for Assessing a Supercritical Geothermal System: Evaluation Using a Numerical Model     

Ishitsuka  Kazuya  Kobayashi  Yosuke  Watanabe  Norihiro  Yamaya  Yusuke  Bjarkason  Elvar  Suzuki  Anna  Mogi  Toru  Asanuma  Hiroshi  Kajiwara  Tatsuya  Sugimoto  Takeshi  Saito  Ryoichi 《Natural Resources Research》2021,30(5):3289-3314

The temperature distribution at depth is a key variable when assessing the potential of a supercritical geothermal resource as well as a conventional geothermal resource. Data-driven estimation by a machine-learning approach is a promising way to estimate temperature distributions at depth in geothermal fields. In this study, we developed two methodologies—one based on Bayesian estimation and the other on neural networks—to estimate temperature distributions in geothermal fields. These methodologies can be used to supplement existing temperature logs, by estimating temperature distributions in unexplored regions of the subsurface, based on electrical resistivity data, observed geological/mineralogical boundaries, and microseismic observations. We evaluated the accuracy and characteristics of these methodologies using a numerical model of the Kakkonda geothermal field, Japan, where a temperature above 500 °C was observed below a depth of about 3.7 km. When using geological and geophysical knowledge as prior information for the machine learning methods, the results demonstrate that the approaches can provide subsurface temperature estimates that are consistent with the temperature distribution given by the numerical model. Using a numerical model as a benchmark helps to understand the characteristics of the machine learning approaches and may help to identify ways of improving these methods.

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Calibration and validation of the ocean color version-3 product from ADEOS OCTS     

Masanobu Shimada  Hiromi Oaku  Yasushi Mitomi  Hiroshi Murakami  Akira Mukaida  Yasuhisa Nakamura  Joji Ishizaka  Hiroshi Kawamura  Tasuku Tanaka  Motoaki Kishino  Hajime Fukushima 《Journal of Oceanography》1998,54(5):401-416

We present calibration and validation results of the OCTS’s ocean color version-3 product, which mainly consists of the chlorophyll-a concentration (Chl-a) and the normalized water-leaving radiance (_nL_w). First, OCTS was calibrated for the inter-detector sensitivity difference, offset, and absolute sensitivity using external calibration source. It was also vicariously calibrated using in-situ measurements for water (Chl-a and_nL_w) and atmosphere (optical thickness), which were acquired synchronously with OCTS under cloud-free conditions. Second, the product was validated using selected 17 in-situ Chl-a and 11 in-situ_nL_w measurements. We confirmed that Chl-a was estimated with an accuracy of 68% for Chl-a less than 2 mg/m³, and_nL_w from 94% (band 2) to 128% (band 4). Geometric accuracy was improved to 1.3 km. Stripes were significantly reduced by modifying the detector normalization factor as a function of input radiance.  相似文献   

MOS-1/1b MESSR Observations of the Antarctic Sea Ice: Ice Bands and Ice Streamers     

Kunimitsu Ishida  Kay I. Ohshima  Takashi Yamanouchi  Hiroshi Kanzawa 《Journal of Oceanography》1999,55(3):417-426

Meso- or submeso-scale features of the Antarctic sea ice are investigated using the MOS-1/1b MESSR Images (spatial resolution of approximately 50 m) received at Syowa Station. Particular attention is paid to the ice bands and ice streamers in coastal polynyas. In the Antarctic Ocean, ice bands can be often seen not only at the ice edge but also in the ice interior zone throughout the year and they extend for hundreds of kilometers in the latitudinal direction. It is found that the width and spacing of ice bands tend to decrease from winter to summer. The width of ice band is about 2–6 km in August and September, and 0.1–0.7 km in December. The spacing of ice bands is about 3–10 km in August and September, and 0.1–2 km in December. In coastal polynyas, ice streamers, which are composed of new ice, are sometimes observed. In general, the row of the streamers is spaced at 0.5–2 km with a width of 0.1–1.0 km.  相似文献   

Simulation of the effect of wind speedup in the formation of transverse dune fields     

Hiroshi Momiji  Ricardo Carretero‐Gonzlez  Steven R Bishop  Andrew Warren 《地球表面变化过程与地形》2000,25(8):905-918

A computer simulation model for transverse‐dune‐field dynamics, corresponding to a uni‐directional wind regime, is developed. In a previous formulation, two distinct problems were found regarding the cross‐sectional dune shape, namely the erosion in the lee of dunes and the steepness of the windward slopes. The first problem is solved by introducing no erosion in shadow zones. The second issue is overcome by introducing a wind speedup (shear velocity increase) factor, which can be accounted for by adding a term to the original transport length, which is proportional to the surface height. By incorporating these features we are able to model dunes whose individual shape and collective patterns are similar to those observed in nature. Moreover we show how the introduction of a non‐linear shear‐velocity‐increase term leads to the reduction of dune height, and this may result in an equilibrium dune field configuration. This is thought to be because the non‐linear increase of the transport length makes the sand trapping efficiency lower than unity, even for higher dunes, so that the incoming and the outgoing sand flux are in balance. To fully describe the inter‐dune morphology more precise dynamics in the lee of the dune must be incorporated. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Response analysis of the Higashi–Kobe Bridge and surrounding soil in the 1995 Hyogoken–Nanbu Earthquake     

Todor Ganev  Fumio Yamazaki  Hiroshi Ishizaki  Masahiko Kitazawa 《地震工程与结构动力学》1998,27(6):557-576

This paper presents results of observation and analysis of the response of one of the longest cable-stayed bridges in the world to the Hyogoken–Nanbu (Kobe) Earthquake of 17 January 1995. It is determined that interaction of the foundations of the bridge towers with the supporting soil plays a decisive role in the overall structural behaviour. The key factor governing the changes of the soil properties at this site is pore-water pressure buildup, which results in liquefaction of the saturated surface soil layers under large dynamic loads. Models of the soil and structure are created and initially validated by accurately simulating the system response to a small earthquake. Soil parameters reflecting the pore-water pressure buildup in the strong earthquake are determined by an advanced non-linear effective stress analysis, combining the Ramberg–Osgood model of stress–strain dependence with a pore pressure model based on shear work concept. They are utilized to investigate and simulate the interaction of the foundation and the supporting soil using the program SASSI with the flexible volume substructuring approach. The results show a good agreement with the observations and have useful implications to the scientific and engineering practice. © 1998 John Wiley & Sons, Ltd.  相似文献   

Dynamic FE simulation of four‐story steel frame modeled by solid elements and its validation using results of full‐scale shake‐table test          下载免费PDF全文

Tomoshi Miyamura  Takuzo Yamashita  Hiroshi Akiba  Makoto Ohsaki 《地震工程与结构动力学》2015,44(9):1449-1469

Dynamic finite element analyses of a four‐story steel building frame modeled as a fine mesh of solid elements are performed using E‐Simulator, which is a parallel finite element analysis software package for precisely simulating collapse behaviors of civil and building structures. E‐Simulator is under development at the National Research Institute for Earth Science and Disaster Prevention (NIED), Japan. A full‐scale shake‐table test for a four‐story frame was conducted using E‐Defense at NIED, which is the largest shaking table in the world. A mesh of the entire structure of a four‐story frame with approximately 19 million degrees of freedom is constructed using solid elements. The density of the mesh is determined by referring to the results of elastic–plastic buckling analyses of a column of the frame using meshes of different densities. Therefore, the analysis model of the frame is well verified. Seismic response analyses under 60, 100, and 115% excitations of the JR Takatori record of the 1995 Hyogoken‐Nanbu earthquake are performed. Note that the simulation does not reproduce the collapse under the 100% excitation of the Takatori record in the E‐Defense test. Therefore, simulations for the 115% case are also performed. The results obtained by E‐Simulator are compared with those obtained by the E‐Defense full‐scale test in order to validate the results obtained by E‐Simulator. The shear forces and interstory drift angles of the first story obtained by the simulation and the test are in good agreement. Both the response of the entire frame and the local deformation as a result of elastic–plastic buckling are simulated simultaneously using E‐Simulator. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Spatial distribution of sister species of vesicomyid bivalves Calyptogena okutanii and Calyptogena soyoae along an environmental gradient in chemosynthetic biological communities in Japan     

Hiromi Watanabe  Eriko Seo  Yoshimi Takahashi  Takao Yoshida  Shigeaki Kojima  Katsunori Fujikura  Hiroshi Miyake 《Journal of Oceanography》2013,69(1):129-134

Vesicomyid bivalves have a substantial biomass in deep-sea chemosynthetic biological communities in the Pacific. Using a novel multiplex-PCR (mPCR) method to identify the co-occurring vesicomyids in Sagami Bay, we analyzed the distribution of Calyptogena okutanii and Calyptogena soyoae along environmental gradients. All the known distributions of C. okutanii indicated the different preferences in salinity and temperature to those of C. soyoae, and in Sagami Bay, depth seemed to be an important environmental factor, too. Although the concentration of hydrogen sulfide in sediment was not examined, our results showed that the distributions of these two Calyptogena clams were affected by salinity and temperature.  相似文献   

Volume transports proceeding to the Kuroshio Extension region and recirculating in the Shikoku Basin   总被引：4，自引：1，他引：3  

Akira Nagano  Kaoru Ichikawa  Hiroshi Ichikawa  Masanori Konda  Kiyoshi Murakami 《Journal of Oceanography》2013,69(3):285-293

The volume transport of the Kuroshio, the western boundary current of the North Pacific subtropical gyre, varies vigorously due to merging of disturbances propagating from the entire North Pacific. Taking into account the recirculation in the Shikoku Basin by the zonal observation line at 30°N to the west of the Izu–Ogasawara Ridge, we estimated the volume transport in the top 1,000 m layer toward the Kuroshio Extension region. The volume transport of the local recirculation gyre in the Shikoku Basin increases associated with the westward extension of the gyre, particularly in the period of the large meandering path of the Kuroshio south of Japan. Meanwhile, most of the transport variations toward the Kuroshio Extension region correspond to those of the Kuroshio transport on the continental slope south of Japan, which vary independently of those of the recirculation gyre.  相似文献   

Large ageostrophic currents in the abyssal layer southeast of Kyushu, Japan, by direct measurement of LADCP   总被引：1，自引：1，他引：0  

Akira Nagano  Kaoru Ichikawa  Hiroshi Ichikawa  Yasushi Yoshikawa  Kiyoshi Murakami 《Journal of Oceanography》2013,69(2):259-268

With full-depth LADCP velocity data collected in a wide area southeast of Kyushu, Japan, large velocity currents, occasionally exceeding 15 cm s^?1, were observed in a thick, 500–1,500 m, near-homogeneous density layer below approximately 3,000 m depth around the steep topographies. The currents were found not to flow along the topographic contours, and to be strongly ageostrophic. The directions of the bottom-layer currents are rather related with phase of the semi-diurnal tides, suggesting deeply intruded internal tides generated at the steep topographies.  相似文献   

Size fraction and class composition of phytoplankton in the Antarctic marginal ice zone along the 140°E meridian during February–March 2003     

Fuminori Hashihama  Toru Hirawake  Sakae Kudoh  Jota Kanda  Ken Furuya  Yukuya Yamaguchi  Takashi Ishimaru 《Polar Science》2008,2(2):109-120

We investigated the size fraction and pigment-derived class compositions of phytoplankton within the euphotic zone of the Antarctic marginal ice zone between 63.3°S and 66.5°S along the 140°E meridian on two consecutive cruises in the late austral summer and early austral autumn of 2003. We observed significant temporal and spatial variations in phytoplankton size and taxonomic composition, although chlorophyll a concentrations were generally below 1 μg l⁻¹ during both periods. Microphytoplankton (>20 μm), mainly diatoms, were prominent in the euphotic zone in the southernmost area around 66.5°S during late summer. In the rest of the study area during both cruises, the phytoplankton community was dominated by pico- and nano-sized populations (<20 μm) throughout the euphotic zone. The small-size populations mostly consisted of diatoms and haptophytes, although chlorophytes were dominant in extremely cold water (−1.5°C) below the overlying warm water around 65.5°S during late summer. From late summer to early autumn, chlorophytes declined in abundance, probably due to increasing temperature within the euphotic zone (−1 to 0°C). These pico- and nano-phytoplankton-dominated populations were often accompanied by relatively high concentrations of ammonium, suggesting the active regeneration of nutrients within the small-size plankton community.  相似文献