Seafloor Geodesy From Repeated Multibeam Bathymetric Surveys: Application to Seafloor Displacement Caused by the 2011 Tohoku-Oki Earthquake

Frontiers in Earth Science ◽

10.3389/feart.2021.667666 ◽

2021 ◽

Vol 9 ◽

Author(s):

Toshiya Fujiwara

Keyword(s):

Horizontal Displacement ◽

Relative Difference ◽

Japan Trench ◽

Bathymetric Survey ◽

Seafloor Geodesy ◽

Bathymetric Data ◽

Rupture Area ◽

Trench Axis ◽

The Difference ◽

Northern Japan

Repeated multibeam bathymetric surveys played an important role for understanding the distribution of coseismic seafloor displacement caused by the March 11, 2011 Mw 9.0 Tohoku-oki earthquake. After the earthquake, we collected bathymetric data along the same tracks obtained before the earthquake. The selected tracks were crossing the trench and extending from the landward to seaward trench slopes. We examined the seafloor displacement on the landward relative to the seaward by means of the difference in bathymetry before and after the earthquake. The multibeam bathymetric survey has the advantage of areal coverage. The repeated surveys clarified the areal distribution of the coseismic seafloor displacement. In the main rupture area, very large seafloor displacement was observed. Sharp bathymetric change at the trench axis provided solid evidence that the fault slip on the shallowest part of the megathrust reached the trench axis and peaked at the trench axis. The very large displacement is limited to the particular area. Smaller seafloor displacements were observed in the area tens of kilometers away from the main rupture area. We present methods and results of the repeated multibeam bathymetric surveys and an application to the seafloor displacement caused by the 2011 Tohoku-oki earthquake in the northern Japan Trench. Less than several meters in seafloor vertical displacements and less than 20 m in seafloor horizontal displacement were estimated in the northern Japan Trench. The estimated smaller displacements are comparable in magnitude to error of the seafloor displacement observation from our bathymetric survey. Nevertheless, three adjacent survey tracks showed coherent relative differences in seafloor elevation, which suggests the relative difference enables us to discuss the along-track variation in seafloor displacement in the area. However, our survey was affected by uncertainties of roll and pitch biases and sound velocity errors. Well-prepared repeated multibeam bathymetric survey for the purpose of seafloor geodesy could lead to a higher resolution and more accurate result. Repeated acquisition of high resolution and accuracy bathymetric data using state-of-the-art technology will be important to quantitative discussion of the seafloor displacements caused by even smaller magnitude earthquakes and tsunamis.

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Seismicity around the trench axis and outer-rise region of the southern Japan Trench, south of the main rupture area of the 2011 Tohoku-oki earthquake

Geophysical Journal International ◽

10.1093/gji/ggab093 ◽

2021 ◽

Vol 226 (1) ◽

pp. 131-145

Author(s):

Koichiro Obana ◽

Gou Fujie ◽

Yojiro Yamamoto ◽

Yuka Kaiho ◽

Yasuyuki Nakamura ◽

...

Keyword(s):

Japan Trench ◽

Normal Faults ◽

The South ◽

Plate Interface ◽

Lower Velocity ◽

Outer Rise ◽

Rupture Area ◽

Trench Axis ◽

Southern Japan ◽

Structure Heterogeneity

SUMMARY The 2011 Mw 9.0 Tohoku-oki earthquake ruptured the subduction megathrust fault in the central Japan Trench. We investigated the aftershock activity in the southern Japan Trench to the south of the main rupture area using ocean bottom seismographs deployed both landward and seaward of the trench. In the trench-outer rise region seaward of the trench axis, we identified several ∼100-km-long linear earthquake trends both parallel and oblique to the southern Japan Trench. The earthquake trend oblique to the southern Japan Trench is a southward extension of the trench-parallel linear earthquake trend in the central to northern Japan Trench. The trench-parallel normal-faults in the trench-outer rise region could extend linearly, despite the change of the trench strike from N–S to NNE–SSW to the south of the main rupture area. Normal-faults oblique to the trench should be considered as substantial parts of large intraplate normal-faulting earthquakes. In addition, intraplate seismicity coinciding with the lower velocity oceanic mantle suggest that the structure heterogeneity would be indicative of normal-faults extending into the mantle. In the trench landward area, earthquake activity showed along-trench variations. Earthquakes along the shallow megathrust interface near the trench were observed south of 37°N. These shallow near-trench regular earthquakes, which are located close to the episodic tremors and temporally correlated with the tremor activities, suggest that the afterslip on the plate interface likely extended to the shallow plate interface close to the trench axis. Smaller spatial scale structure heterogeneity, such as the thickness variation in the channel-like low-velocity sedimentary unit, likely relate to the proximity of the regular earthquakes and slow slip which results in the formation of diverse slip behaviours in the shallow subduction zone of the southern Japan Trench.

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Development of Simulation Program for Temperature Field of Mass Concrete Structures

E3S Web of Conferences ◽

10.1051/e3sconf/20183803020 ◽

2018 ◽

Vol 38 ◽

pp. 03020 ◽

Cited By ~ 1

Author(s):

Zheng Si ◽

Qian Zhang ◽

Ling Zhi Huang ◽

Dan Yang

Keyword(s):

Temperature Field ◽

Concrete Structure ◽

Relative Difference ◽

Maximum Temperature ◽

Mass Concrete ◽

Field Calculation ◽

Concrete Dam ◽

Roller Compacted Concrete ◽

Roller Compacted Concrete Dam ◽

The Difference

Most existing temperature field calculation programs have relative defects. In the present paper, based on merits of ANSYS platform, a temperature field calculation program of mass concrete structure is developed and demonstrated. According to actual pouring progress and thermodynamic parameters, a roller-compacted concrete dam is simulated. The difference of maximum temperature between calculated and measured values of measuring points is less than 1.8°C. Furthermore, the relative difference is -5%–5%. This result shows that the calculation program developed based on ANSYS platform can simulate and calculate the temperature field of mass concrete structure.

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Along‐trench variations in the seismic structure of the incoming Pacific plate at the outer rise of the northern Japan Trench

Geophysical Research Letters ◽

10.1002/2015gl067363 ◽

2016 ◽

Vol 43 (2) ◽

pp. 666-673 ◽

Cited By ~ 19

Author(s):

Gou Fujie ◽

Shuichi Kodaira ◽

Takeshi Sato ◽

Tsutomu Takahashi

Keyword(s):

Pacific Plate ◽

Japan Trench ◽

Seismic Structure ◽

Outer Rise ◽

Northern Japan

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Crisp and Fuzzy AHP in GIS-MCDA for Wildlife Habitat Suitability Analysis

Advances in Environmental Engineering and Green Technologies - Spatial Information Science for Natural Resource Management ◽

10.4018/978-1-7998-5027-4.ch001 ◽

2020 ◽

pp. 1-23

Author(s):

Suman Sinha

Keyword(s):

Habitat Suitability ◽

Fuzzy Ahp ◽

Relative Difference ◽

Suitability Analysis ◽

Value Judgments ◽

Analytic Hierarchy ◽

Chi Square ◽

Chi Square Test ◽

The Difference ◽

Wildlife Reserve

Geographic information system-based multi-criteria decision analysis (GIS-MCDA) is a process of decision making where geographical data and value judgments are integrated. Analytic hierarchy process (AHP) is a useful technique in MCDA for determining weights. This study focuses on the evaluation of GIS-MCDA using different uncertainty levels in AHP. Best suitable sites for tiger habitats are located and analyzed in Sariska Wildlife Reserve, India using crisp and fuzzy AHP in GIS-MCDA, and thereafter, an optimal habitat suitability model is proposed. The percentage deviation over the uncertainty levels ranges slightly over 5%. The relative difference between CAHP and FAHP is nearly 2.7%. Chi-square test reveals relationship between the degree of uncertainty and the difference between the maps. For real-world situations with increased variability, fuzzification is preferred and shows the best results. The worldwide declining status of the tigers is a serious threat to the overall biodiversity, and the methods adopted in this study thus target their conservation and management.

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Analysis of the Use of Geomorphic Elements Mapping to Characterize Subaqueous Bedforms Using Multibeam Bathymetric Data in River System

Applied Sciences ◽

10.3390/app10217692 ◽

2020 ◽

Vol 10 (21) ◽

pp. 7692

Author(s):

Ge Yan ◽

Heqin Cheng ◽

Lizhi Teng ◽

Wei Xu ◽

Yuehua Jiang ◽

...

Keyword(s):

Fluvial Geomorphology ◽

River System ◽

Self Organization ◽

Classification Methods ◽

Optimal Method ◽

Feature Description ◽

Bathymetric Data ◽

The Difference ◽

The Stability ◽

Underwater Structures

Riverbed micro-topographical features, such as crest and trough, flat bed, and scour pit, indicate the evolution of fluvial geomorphology, and have an influence on the stability of underwater structures and overall scour pits. Previous studies on bedform feature extraction have focused mainly on the rhythmic bed surface morphology and have extracted crest and trough, while flat bed and scour pit have been ignored. In this study, to extend the feature description of riverbeds, geomorphic elements mapping was used by employing three geomorphic element classification methods: Wood’s criteria, a self-organization map (SOM) technique, and geomorphons. The results showed that geomorphic element mapping can be controlled by adjusting the slope tolerance and curvature tolerance of Wood’s criteria, using the map unit number and combination of the SOM technique and the flatness of geomorphons. Relatively flat bed can be presented using “plane”, “flat planar”, and “flat” elements, while scour pit can be presented using a “pit” element. A comparison of the difference between parameter settings for landforms and bedforms showed that SOM using 8 or 10 map units is applicable for land and underwater surface and is thus preferentially recommended for use. Furthermore, the use of geomorphons is recommended as the optimal method for characterizing bedform features because it provides a simple element map in the absence of area loss.

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The effects of live weight at weaning on growth rate and carcass composition at different stages of maturity in Scottish Blackface lambs fed on two different diets

Animal Science ◽

10.1017/s0003356100003548 ◽

1988 ◽

Vol 47 (3) ◽

pp. 401-409 ◽

Cited By ~ 10

Author(s):

J. M. Doney ◽

J. A. Milne ◽

T. J. Maxwell ◽

Angela M. Sibbald ◽

A. D. M. Smith

Keyword(s):

Weight Gain ◽

Live Weight ◽

Relative Difference ◽

Carcass Composition ◽

Metabolizable Energy ◽

Energy Ratio ◽

Weaning Weight ◽

Slaughter Weight ◽

Protein Energy ◽

The Difference

ABSTRACTThe effects of live weight at weaning on carcass composition were studied with 104 Scottish Blackface lambs offered two diets differing in protein: energy ratio. Groups of lambs were slaughtered at initial live weights of 24·1 (s.e. 1·48) kg (LL) and 28·9 (s.e. 1·67) kg (IL) and at 33 kg, 38 kg, 43 kg, 53 kg and mature live weight.Lambs were offered two diets — low protein: energy ratio (LP, 122 g crude protein (CP) per kg dry matter (DM): 10·4 MJ metabolizable energy (ME) per kg DM) and high protein: energy ratio (HP, 176 g CP per kg DM: 10·4 MJ ME per kg DM). The LP diet was offeredad libitumand the HP diet was restricted to a similar mean level. Muscle, fat and bone tissues in the carcass were separated and weighed and the carcass and non-carcass component tissues were analysed for chemical fat, protein and ash.Daily live-weight gain (DLWG) of HP lambs (148 (s.e. 8·1) g/day) was significantly higher than that of LP lambs (118 (s.e. 8·1) g/day;P< 0·05) and food conversion ratios were lower up to a live weight of 43 kg (P< 0·05). There were no differences in intake or DLWG between LL and IL lambs. Mature live weight (73·3 (s.e. 1·79) kg) was not related to weaning weight or post-weaning diet.There was no effect of diet on carcass composition at any slaughter weight but LL lambs had a higher fat proportion than IL lambs, which was significant (P< 0·05) at 33 kg only. During the feeding period, the increment of fat tissue per unit increase in live weight (348 (s.e. 15·8) g/kg LW) was not affected by live weight at the start of the diet. The difference between LL and IL lambs in fat proportion was directly related to the difference in weight gain required to reach slaughter weight. The difference was not a function of stage of maturity but only of weaning weight, itself largely determined by pre-weaning nutrition. At higher slaughter weights the relative difference decreased and became non-significant. Hence lambs lighter at weaning would be less suitable than heavier lambs for the production of light-weight lean carcasses.

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A Numerical Study of Tsunami Generation by Horizontal Displacement of Sloping Seafloor

Journal of Earthquake and Tsunami ◽

10.1142/s1793431120500189 ◽

2020 ◽

Vol 14 (04) ◽

pp. 2050018 ◽

Cited By ~ 1

Author(s):

Chentong Hu ◽

Yifan Wu ◽

Chao An ◽

Hua Liu

Keyword(s):

Numerical Study ◽

Horizontal Displacement ◽

Vertical Displacement ◽

Horizontal Motion ◽

Generation Process ◽

Tsunami Generation ◽

Initial Water ◽

Horizontal Momentum ◽

The Difference ◽

Water Elevation

Tsunamis are generated primarily by the vertical displacement of the seafloor if the seafloor is flat. If the seafloor is slanted, the horizontal motion also contributes to the generation of tsunamis. A previous study proposed that such effects can be estimated by simply calculating the elevation of water due to the horizontal displacement of the slope. Two more studies later argued that the horizontal motion also results in horizontal momentum of the water, which amplifies the tsunami generation. In this study, we numerically simulate the tsunami generation process of flat and sloping seafloor. It is found that, for the flat seafloor, the initial water elevation equals the vertical seafloor displacement. For the sloping seafloor, the initial water elevation deviates from the vertical seafloor displacement, and the difference can be accurately evaluated by the horizontal seafloor displacement. Thus, the initial horizontal momentum of the water is negligible for tsunami generation.

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Utilization of gastropod shells by hermit crabs (Decapoda: Anomura: Paguridae) in Japan as related to characteristics of domicile shell

Journal of Crustacean Biology ◽

10.1093/jcbiol/ruaa092 ◽

2020 ◽

Author(s):

Satoshi Takeda

Keyword(s):

Shell Thickness ◽

Compressive Force ◽

Hermit Crabs ◽

Gastropod Species ◽

The Difference ◽

De Man ◽

Northern Japan

Abstract The relative proportions of gastropod shells occupied by the hermit crabs Pagurus dubius (Ortmann, 1892), P. filholi (De Man, 1887), P. lanuginose De Haan, 1849, and P. nigrofascia Komai, 1996 on a boulder shore at Asamushi, northern Japan differ significantly from those of the living gastropods that leave behind their empty shells after death. There is a difference in the frequencies of the shells of Omphalius rusticus (Gmelin, 1791) and Chlorostoma turbinatum A. Adams, 1853, which resemble each other in shape, between the proportions of shells occupied by the living gastropods and those of their empty shells occupied by hermit crabs. The three species of hermit crabs that were dominant at the study site showed no difference in shell selectivity between the two gastropod species in the laboratory. This result indicates that shell selection by hermit crabs cannot be responsible for the difference in composition between availability and utilization observed in the field. The empty shells of O. rusticus are thicker and heavier than those of C. turbinatum, suggesting that the former last longer than the latter, as shell durability against compressive force decreases as shell thickness is reduced. These observations suggest that the difference in the period for which these empty gastropod shells remain intact accounts for the difference in composition between their availability and utilization by hermit crabs.

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