Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not cl...Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not clear.Here we study the problem by simulation using a new approach of the spectral-element method with some overlapped elements（SEMO） that can accurately evaluate waves traveling along an irregular interface.Consequently,the head waves are separated from interface waves by a time window.Thus,their energy and arrival time changes can be analyzed independently.These analyses demonstrate that,contrary to the case for head waves propagating along a flat interface,there are two mechanisms for head waves traveling along an irregular interface：a refraction mechanism and transmission mechanism.That is,the head waves may be refracted waves propagating along the interface or transmitted waves induced by the waves propagating in the higher-velocity media.Such knowledge will be helpful in constructing a more accurate inversion method,such as head wave travel-time tomography,and in obtaining a more accurate model of subsurface structure which is very important for understanding the formation mechanism of some special areas,such as the Tibetan Plateau.展开更多
This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading ang...This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed.A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation.The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles.The full-scale measurements from three different types of ships,i.e.,a PCTC,a container ship,and a chemical tanker,are used to validate the proposed model for speed loss prediction in irregular waves.The effect of the improved model for speed loss prediction on a ship’s voyage optimization is also investigated.The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves.展开更多
This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves....This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.展开更多
Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR1...Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.展开更多
Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seism...Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seismological domain. The present research status of fault-zone head wave and trapped wave are summarized systematically. Based on recent progress in this field,the paper discusses the prospect on the utilization of seismic wave in fault structure research.展开更多
The authors previously introduced a semi-empirical formula that enabled fast estimation of the added resistance of ships in head waves, and in this study the formula is further refined for easy use in engineering appl...The authors previously introduced a semi-empirical formula that enabled fast estimation of the added resistance of ships in head waves, and in this study the formula is further refined for easy use in engineering applications. It includes an alternative ship draft correction coefficient, which better accounts for the wave pressure decay with ship’s draft. In addition, it only uses the speed and main characteristics of the ship and wave environment as input, and has been simplified to the extent that it can be readily processed using a pocket calculator. Extensive validations are conducted for different ship types at low to moderate speeds in various typical irregular sea conditions, and encouraging results are obtained. This relevant and topical research lies within the framework of the recent IMO MEPC.232（65） （2013） EEDI guidelines for estimating the minimum powering of ships in adverse weather conditions, which specify for the use of simple methods in current Level 2 assessment within engineering applications.Keywords： added resistance, minimum power, IMO regulation, EEDI regulation, weather coefficient, semi-empirical formulas, ships, head waves展开更多
Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave lin...Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.展开更多
A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap alo...A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap along the Sagaing Fault.Here we focus on the mainshock rupture properties based on backprojection of teleseismic P waves and early aftershock locations,analysis of near-field seismic recordings for the mainshock initiation,and remotely triggered seismicity following the MW 7.7 mainshock.We find that the~500 km mainshock rupture can be revealed by both rapid back-projection of teleseismic P waves from multiple broadband arrays and early aftershock locations within about 3 h from the Thai Meteorological Department(TMD)catalog.The rupture speed went supershear in the southward propagation after the initial bilateral subshear ruptures,as expected for large strike-slip earthquakes of such sizes.Clear fault zone head waves that are reflected along a bimaterial fault interface are observed at the only near-fault station GE.NPW on the slower side about 2.6 km away from the Sagaing fault,consistent with the preferred direction of a supershear rupture propagating to the south.In addition,aftershocks from the regional TMD catalog appear to be located mostly to the east of the mainshock rupture.While we cannot completely rule out mis-locations from the one-sided station distribution,these off-fault seismicity could also be explained by reactivations of subsidiary faults within the Shan Plateau,or an eastward dipping of the mainshock rupture plane.Although no immediate foreshocks were found from several nearby stations,we identify one sub-event with magnitude~6 at the beginning of the mainshock with a slightly different focal mechanism about 20–30 km south of the hypocenter determined by the United States Geological Survey(USGS).The mainshock also occurred when the tidal stresses reached its maximum on the right-lateral strike-slip fault,likely indicating that the timing of the mainshock is modulated by the solid earth tides.We find a significant increase of seismic activity near the Thailand/Myanmar border,in multiple(geothermally active)regions of Yunnan province in Southwest China,as well as the Xingfengjian reservoir in the Guangdong province in South China.Because static stress changes from the mainshock are small but negative near the Thailand/Myanmar border,the occurrence of microseismicity in this and other regions can be mainly explained by remote triggering from dynamic stress changes of the mainshock rupture.Our analyses demonstrate the importance of rapid analysis on openly available seismic data and catalog to better understand the rupture properties and triggered seismicity following large earthquakes.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.40874027,90715020,and 90915012)the Institute of Geophysics of the China Earthquake Administration (Grant No.DQJB07B06)Special Public Welfare Industry (Grant Nos.20070804 and 200808008)
文摘Head waves are usually considered to be the refracted waves propagating along flat interfaces with an underlying higher velocity.However,the path that the rays travel along in media with irregular interfaces is not clear.Here we study the problem by simulation using a new approach of the spectral-element method with some overlapped elements（SEMO） that can accurately evaluate waves traveling along an irregular interface.Consequently,the head waves are separated from interface waves by a time window.Thus,their energy and arrival time changes can be analyzed independently.These analyses demonstrate that,contrary to the case for head waves propagating along a flat interface,there are two mechanisms for head waves traveling along an irregular interface：a refraction mechanism and transmission mechanism.That is,the head waves may be refracted waves propagating along the interface or transmitted waves induced by the waves propagating in the higher-velocity media.Such knowledge will be helpful in constructing a more accurate inversion method,such as head wave travel-time tomography,and in obtaining a more accurate model of subsurface structure which is very important for understanding the formation mechanism of some special areas,such as the Tibetan Plateau.
基金Open access funding provided by Chalmers University of Technology.The authors acknowledge the financial support from the European Commission(Horizon 2020)project EcoSail(Grant Number 820593)We are also grateful to the support from the Swedish Foundation for International Cooperation in Research and Higher Education(CH2016-6673)+1 种基金National Natural Science Foundation of China(NSFC-51779202)The second author thanks the funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie(Grant Number 754412)and VGR MoRE2020.
文摘This paper proposes a semi-empirical model to predict a ship’s speed loss at arbitrary wave heading.In the model,the formulas that estimate a ship’s added resistance due to waves attacking from different heading angles have been further developed.A correction factor is proposed to consider the nonlinear effect due to large waves in power estimation.The formulas are developed and verified by model tests of 5 ships in regular waves with various heading angles.The full-scale measurements from three different types of ships,i.e.,a PCTC,a container ship,and a chemical tanker,are used to validate the proposed model for speed loss prediction in irregular waves.The effect of the improved model for speed loss prediction on a ship’s voyage optimization is also investigated.The results indicate that a ship’s voyage optimization solutions can be significantly affected by the prediction accuracy of speed loss caused by waves.
文摘This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.
文摘Reynold＇s averaged Navier-Stokes based CFD （computational fluid dynamics） technique WISDAM developed at The University of Tokyo is used to investigate and compare the hydrodynamic loads on container ship models SR108 and KCS in 120 degree regular oblique wave conditions. WISDAM has the capability of handling 6DOF （six degrees of freedom） in ship motions. Finite volume method with structured and overlapping grid system is employed. The flow variables are described in staggered manner, i.e., velocity components arc defined at the face center while pressure is at the cell center. Computational results agree favorably well with existing towing tank results especially for ship motions. Computational results also show that ship with bulbous bow experience higher hydrodynamic loads on bow section.
基金sponsored by the Foundation of China Scholarship Council,the"Earthquake Science Talents Training Program"of China Earthquake Administration,the Sub-project of National Key Technology R&D Program(1012BAK19804-01-05)the Natural Science Foundation of Shandong Province(ZR2012DQ006),China
文摘Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seismological domain. The present research status of fault-zone head wave and trapped wave are summarized systematically. Based on recent progress in this field,the paper discusses the prospect on the utilization of seismic wave in fault structure research.
基金Partly Supported by the Collaborative Project SHOPERA under Grant Agreement No.605221
文摘The authors previously introduced a semi-empirical formula that enabled fast estimation of the added resistance of ships in head waves, and in this study the formula is further refined for easy use in engineering applications. It includes an alternative ship draft correction coefficient, which better accounts for the wave pressure decay with ship’s draft. In addition, it only uses the speed and main characteristics of the ship and wave environment as input, and has been simplified to the extent that it can be readily processed using a pocket calculator. Extensive validations are conducted for different ship types at low to moderate speeds in various typical irregular sea conditions, and encouraging results are obtained. This relevant and topical research lies within the framework of the recent IMO MEPC.232（65） （2013） EEDI guidelines for estimating the minimum powering of ships in adverse weather conditions, which specify for the use of simple methods in current Level 2 assessment within engineering applications.Keywords： added resistance, minimum power, IMO regulation, EEDI regulation, weather coefficient, semi-empirical formulas, ships, head waves
基金financially supported by the National Key R&D Program of China (Grant No.2021YFC3100700)the National Natural Science Foundation of China (Grant Nos.U2039209 and 41874067)the Natural Science Foundation of Heilongjiang Province,China (Grant No.YQ2021D010)。
文摘Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.
基金supported by National Science Foundation Grant RISE-2425889supported by Earthquake Prediction Open Fund,China Earthquake Administration(Grant No.XH25006D)supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.164GJHZ2023006MI).
文摘A devastating MW 7.7 earthquake struck near Mandalay,Myanmar,on March 28,2025,causing extensive damage and casualties across Myanmar and neighboring regions.The 2025 event occurred in a well-recognized seismic gap along the Sagaing Fault.Here we focus on the mainshock rupture properties based on backprojection of teleseismic P waves and early aftershock locations,analysis of near-field seismic recordings for the mainshock initiation,and remotely triggered seismicity following the MW 7.7 mainshock.We find that the~500 km mainshock rupture can be revealed by both rapid back-projection of teleseismic P waves from multiple broadband arrays and early aftershock locations within about 3 h from the Thai Meteorological Department(TMD)catalog.The rupture speed went supershear in the southward propagation after the initial bilateral subshear ruptures,as expected for large strike-slip earthquakes of such sizes.Clear fault zone head waves that are reflected along a bimaterial fault interface are observed at the only near-fault station GE.NPW on the slower side about 2.6 km away from the Sagaing fault,consistent with the preferred direction of a supershear rupture propagating to the south.In addition,aftershocks from the regional TMD catalog appear to be located mostly to the east of the mainshock rupture.While we cannot completely rule out mis-locations from the one-sided station distribution,these off-fault seismicity could also be explained by reactivations of subsidiary faults within the Shan Plateau,or an eastward dipping of the mainshock rupture plane.Although no immediate foreshocks were found from several nearby stations,we identify one sub-event with magnitude~6 at the beginning of the mainshock with a slightly different focal mechanism about 20–30 km south of the hypocenter determined by the United States Geological Survey(USGS).The mainshock also occurred when the tidal stresses reached its maximum on the right-lateral strike-slip fault,likely indicating that the timing of the mainshock is modulated by the solid earth tides.We find a significant increase of seismic activity near the Thailand/Myanmar border,in multiple(geothermally active)regions of Yunnan province in Southwest China,as well as the Xingfengjian reservoir in the Guangdong province in South China.Because static stress changes from the mainshock are small but negative near the Thailand/Myanmar border,the occurrence of microseismicity in this and other regions can be mainly explained by remote triggering from dynamic stress changes of the mainshock rupture.Our analyses demonstrate the importance of rapid analysis on openly available seismic data and catalog to better understand the rupture properties and triggered seismicity following large earthquakes.
