• Title/Summary/Keyword: bathymetry

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Bathymetry Change Investigation of the 2011 Tohoku Earthquake

  • Kim, Kwang Bae;Lee, Chang Kyung
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.33 no.3
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    • pp.181-192
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    • 2015
  • Bathymetry change due to the 2011 Tohoku (M9.0) earthquake was investigated through satellite altimetry-derived free-air gravity anomalies (SAFAGA) and shipborne measurements. The earthquake occurred at the plate boundaries near the northeastern coast of Japan, where the oceanic plate subducts beneath the continental plate along deep-sea trench. Data analyzed in this study include SAFAGA from Scripps Institution of Oceanography (SIO), shipborne bathymetry (SB) from the U.S. National Geophysical Data Center (NGDC) and the Japan Agency for Marine-Earth-Science And Technology (JAMSTEC). To estimate the bathymetry change, a reference bathymetry before the earthquake was predicted by gravity-geologic method (GGM) and Smith & Sandwell’s (SAS) method. In comparison with the bathymetry models before the earthquake, GGM bathymetry model generated by a tuning density contrast of 17.04 g/cm3 by downward continuation method was selected because it shows better bathymetry in the short wavelength below about 6 km. From the results, remarkable bathymetry change of about ±50 m was found on the west side of the Japan Trench caused by the earthquake.

Numerical Analysis of Floating-Body Motions in Varying Bathymetry

  • Kim, Taeyoung;Kim, Yonghawn
    • International Journal of Ocean System Engineering
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    • v.4 no.1
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    • pp.43-48
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    • 2014
  • Varying bathymetry significantly affects on the wave propagation and motion response of floating body. Coupled-mode wave theory is adopted to describe the incident wave properly in varying region. The results of waves and motion response are compared to those from numerical wave tank, and the agreement is favorable. The sloped bottom is modeled and its effect on the floating body is discussed.

Generation Method of Bathymetry for the Numerical Model (수치모형을 위한 수심도 생성기법)

  • Moon, Seung Rok;Park, Seon Jung;Kang, Ju Whan
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.496-499
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    • 2004
  • 컴퓨터와 다양한 software의 보급과 함께 흐름의 수치해석 분야는 급속한 발전을 보게 되었고 고도의 수치해법이나 복잡한 경계 처리 등을 통해 실제현상과 같은 흐름해석을 가능케 하고 있으며, 이러한 수치해석을 위해 정확한 Bathymetry는 필수적이다. 본 연구에서는 등 격자간격의 수심도 생성을 위하여 전자해도를 작업에 적합하게 수정하고 부족한 조간대의 수심자료는 보완하고, 파일형식에 따른 적절한 프로그램밍 언어를 통하여 해도상 지점들의 수심자료를 획득하고 내삽하여 기존에 사용되는 방법에 비하여 비교적 간단하고 해도의 정보를 정확하게 반영하는 Bathymetry를 생성하는 기법을 제안하였다.

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Numerical Simulations of the 2011 Tohoku, Japan Tsunami Forerunner Observed in Korea using the Bathymetry Effect (지형효과를 이용한 한반도에서 관측된 2011년 동일본 지진해일 선행파 수치모의)

  • Lee, Jun-Whan;Park, Eun Hee;Park, Sun-Cheon;Lee, Duk Kee;Lee, Jong Ho
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.28 no.5
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    • pp.265-276
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    • 2016
  • The 2011 Tohoku, Japan Tsunami, which occurred on March 11, 2011, reached the Korean Peninsula and was recorded at numerous tide stations. In the records of the north-eastern tide stations, tsunami forerunners were found in only about a few minutes after the earthquake, which was much earlier than the expected arrival time based on a numerical simulation. Murotani et al. (2015) found out that the bathymetry effect is related to the tsunami forerunners observed in Japan and Russia. In this study, the tsunami forerunners observed in Korea were well reproduced by a numerical simulation considering the bathymetry effect. This indicates that it is important to consider the bathymetry effect for a tsunami caused by an earthquake on shallowly dipping fault plane(e.g. 2011 Tohoku, Japan Earthquake). However, since the bathymetry effect requires additional computation time, it is necessary to examine the problems that results from applying the bathymetry effect to the tsunami warning system.

Gravity-Geologic Prediction of Bathymetry in the Drake Passage, Antarctica (Gravity-Geologic Method를 이용한 남극 드레이크 해협의 해저지형 연구)

  • 김정우;도성재;윤순옥;남상헌;진영근
    • Economic and Environmental Geology
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    • v.35 no.3
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    • pp.273-284
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    • 2002
  • The Gravity-Geologic Method (GGM) was implemented for bathymetric determinations in the Drake Passage, Antarctica, using global marine Free-air Gravity Anomalies (FAGA) data sets by Sandwell and Smith (1997) and local echo sounding measurements. Of the 6548 bathymetric sounding measurements, two thirds of these points were used as control depths, while the remaining values were used as checkpoints. A density contrast of 9.0 gm/㎤ was selected based on the checkpoints predictions with changes in the density contrast assumed between the seawater and ocean bottom topographic mass. Control depths from the echo soundings were used to determine regional gravity components that were removed from FAGA to estimate the gravity effects of the bathymetry. These gravity effects were converted to bathymetry by inversion. In particular, a selective merging technique was developed to effectively combine the echo sounding depths with the GGM bathymetiy to enhance high frequency components along the shipborne sounding tracklines. For the rugged bathymetry of the research area, the GGM bathymetry shows correlation coefficients (CC) of 0.91, 0.92, and 0.85 with local shipborne sounding by KORDI, GEODAS, and a global ETOPO5 model, respectively. The enhanced GGM by selective merging shows imploved CCs of 0.948 and 0.954 with GEODAS and Smith & Sandwell (1997)'s predictions with RMS differences of 449.8 and 441.3 meters. The global marine FAGA data sets and other bathymetric models ensure that the GGM can be used in conjunction with shipborne bathymetry from echo sounding to extend the coverage into the unmapped regions, which should generate better results than simply gridding the sparse data or relying upon lower resolution global data sets such as ETOPO5.

Development of Topological Correction Algorithms for ADCP Multibeam Bathymetry Measurements (ADCP 다중빔 수심계측자료의 위상학적 보정 알고리즘 개발)

  • Kim, Dong-Su;Yang, Sung-Kee;Kim, Soo-Jeong;Jung, Woo-Yul
    • Journal of Environmental Science International
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    • v.22 no.5
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    • pp.543-554
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    • 2013
  • Acoustic Doppler Current Profilers (ADCPs) are increasingly popular in the river research and management communities being primarily used for estimation of stream flows. ADCPs capabilities, however, entail additional features that are not fully explored, such as morphological representation of river or reservoir bed based upon multi-beam depth measurements. In addition to flow velocity, ADCP measurements include river bathymetry information through the depth measurements acquired in individual 4 or 5 beams with a given oblique angle. Such sounding capability indicates that multi-beam ADCPs can be utilized as an efficient depth-sounder to be more capable than the conventional single-beam eco-sounders. The paper introduces the post-processing algorithms required to deal with raw ADCP bathymetry measurements including the following aspects: a) correcting the individual beam depths for tilt (pitch and roll); b) filtering outliers using SMART filters; d) transforming the corrected depths into geographical coordinates by UTM conversion; and, e) tag the beam detecting locations with the concurrent GPS information; f) spatial representation in a GIS package. The developed algorithms are applied for the ADCP bathymetric dataset acquired from Han-Cheon in Jeju Island to validate themselves applicability.

A Geostatistical Study for the Selection of Prospective Areas of Polymetallic Nodule Deposits (망간단괴광상의 유망광구선정을 위한 지구통계학적 연구)

  • Park, Chan Young;Chon, Hyo Taek;Kang, Jung Keuk
    • Economic and Environmental Geology
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    • v.29 no.5
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    • pp.575-587
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    • 1996
  • The purpose of this study is to develop geostatistical methods for selection of prospective areas of polymetallic nodule deposits in KODOS (Korea Deep Ocean Study) area of the North-East Pacific Ocean. In this study $110{\times}165$ grid system was used, and each node represents the center of an estimated block of $1km{\times}1km$. The ordinary kriging was applied to SeaBeam2000 data in order to evaluate the bathymetry. A structural analysis (variogram) of the bathymetry data was carried out for constructing digital terrain model (DTM) and the maximum slopes of the bathymetry were calculated by DTM data. The above method can be used to solve the problem that is resulted from the lack of theory of a change of support model for the maximum slope of the bathymetry. The ordinary kriging and the indicator kriging were used to evaluate the nodule abundance, and the different two kriging methods were compared to evaluate the accuracy for the estimation of the nodule abundance. It has been shown that indicator kriging was better estimation tool than the ordinary kriging. The overlay map is presented for the selection of potentially minable sites by combining the two indicator maps of the nodule abundance and the maximum slope of bathymetry. This overlay map could be utilized to establish follow-up survey and to investigate the potentially minable sites in the KODOS area.

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Topography in intertidal zone by satellite images

  • Kang, Yong-Q.
    • Proceedings of the KSRS Conference
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    • 2002.10a
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    • pp.664-669
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    • 2002
  • Intertidal zone (tidal flat) is a place which is sometimes dry and sometimes wet depending on the tidal rhythm. Direct measurement of topography in the intertidal zone is very difficult to be achieved. The interface between wet and dry parts in the tidal flat, which can be identified from near infrared band of satellite image, is a 'depth contour' which corresponds to the sea level at the time of satellite pass. Aquisition of topography data in tidal flat is possible by combining various techniques such as (1) identification of the interface between wet and dry parts, (2) GCP correction of satellite image, and (3) realtime prediction of sea level elevation at the time of satellite pass. The algorithm was successfully applied in obtaining topography (bathymetry) data in the intertidal zone of Asan Bay in the west coast of Korea from 26 satellite images. The method is expected to be very efficient in making bathymetry data base in the western and southern parts of Korea where tidal flats are well developed in wide regions.

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UTLIZATION OF FUZZY AND VOLETTRA ALGORITHM FOR 3D BATHYMETRY SIMULATION FROM TOPSAR POLARISED DATA

  • Marghany, Maged;Hussien, Mohd. Lokman
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.432-434
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    • 2003
  • The main objective of this research is to utilize the parallel Fuzzy arithmetic for constructing ocean bathymetry from polarized remote sensing data such as TOPSAR image. In doing so, the parallel library for Fuzzy arithmetic has been developed. Three- dimensional surface modeling consisted of Volettra model, non-linear model which construct a global topological structure between the data points, used to support an approximation of real surface. The output of the parallel library was a digital terrain model for bathymetry along the coastal waters of Kuala Terengganu Malaysia. This paper describes the principles behind the Fuzzy algorithm, indicates for what type of application it might be useful, notes on the accuracy and gives an example of an application.

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Study of the Tidal Channels Appeared on SAR Images

  • Kim, Tae-Rim;Park, Jong-Jib;Choi, Byoung-Ju
    • Korean Journal of Remote Sensing
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    • v.25 no.6
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    • pp.501-505
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    • 2009
  • Quasi-linear bright features persistently appeared on ENVISAT ASAR images as well as X-SAR images along the tidal channels in Gyung-Gi Bay, Korea during the ebb tides. These features are induced by spatial backscatter variations caused by surface convergence (divergence) through the interaction between tidal currents and bathymetry. In order to validate this mechanism, a numerical tidal model simulation is performed on the realistic bathymetry with the tidal boundary conditions. The tide model reproduces the current convergence zone along the tidal channel during the ebb tides, which exactly coincides with the location of bright line features on SAR images.