In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve th...In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.展开更多
Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk.It uses coastal ecosystems such as mangrove forests to create resilient ...Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk.It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection.However,to use mangroves effectively as a nature-based measure for flood risk reduction,we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure.In this perspective,we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence.We show that the forest properties that comprise coastal flood protection are well-known,but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation.Overall,there is relatively good understanding of the ecological processes that drive forest structure and size,but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics,and on the role of combined stressors influencing forest retreat.Integrating simulation models of forest structure under changing physical(e.g.due to sea-level change)and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection.展开更多
A terahertz(THz)wave transmitted through vegetation experiences both absorption and scattering caused by the air molecules and leaves.This paper presents the scattering attenuation characteristics of vegetation in a T...A terahertz(THz)wave transmitted through vegetation experiences both absorption and scattering caused by the air molecules and leaves.This paper presents the scattering attenuation characteristics of vegetation in a THz range.The theoretical path loss model near the vegetation yields the average attenuation of THz waves in a mixed channel composed of air and vegetation leaves.Furthermore,a simplified model of the vegetation structure is obtained for generic vegetation types based on a variety of parameters,such as leaf size,distribution,and moisture content.Finally,based on specific vegetation species and different levels of air humidity,the attenuation characteristics under different conditions are calculated,and the influence of different model parameters on the attenuation characteristics is obtained.展开更多
Recordings of seismic waves propagating from earthquake source to a station at the earth’s surface are a system response function. The convolution operator in time domain can be simplified as a multiplication operato...Recordings of seismic waves propagating from earthquake source to a station at the earth’s surface are a system response function. The convolution operator in time domain can be simplified as a multiplication operator in frequency domain. We discuss in frequency domain the separation of source, path and site effects for global scaling of earthquake source radiation. Also discussed are source scaling model, faulting mechanism, and the H/V inversion problems with crustal and near surface structures. Gross features of apparent source spectra appear to be not much region dependent although there may be difference between tectonic styles within a region of tectonic mixture for which we need further study as data accumulate. Vertical spectra may be a better approach to approximate source radiation, as it has less crustal amplification effects than horizontal spectra. The H/V ratio is evidently a comprehensive indicator of amplification effects from near surface to deep structure. This gives it potential as an inversion tool to deduce site crustal structure.展开更多
基金Research supported by the 863 Program of China(No.2012AA09A20103)the National Natural Science Foundation of China(No.41274119,No.41174080,and No.41004041)
文摘In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.
基金supported by the Joint Research Project Sustainable Deltas co-funded by the National Natural Science Foundation of China(NSFCGrant No.51761135022)+11 种基金the Dutch Research Council(NWOGrant No.ALWSD.2016.026)the Engineering and Physical Sciences Research Council(EPSRCGrant No.EP/R024537/1)the National Natural Science Foundation of China(Grant No.42176202)the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory,Zhuhai(Grant No.311021004)the Guangdong Provincial Department of Science and Technology(Grant No.2019ZT08G090)the 111 Project(Grant No.B21018)the ERC H2020 ESTUARIES Project(Grant No.647570)the Horizon 2020 Marie Skłodowska-Curie Actions Individual Fellowship(Grant No.896888)the China Scholarship Council(Grant No.201706710005)the NWO“LIVING DIKES e Realising Resilient and Climate-Proof Coastal Protection”Project(Grant No.NWA.1292.19.257)。
文摘Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk.It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection.However,to use mangroves effectively as a nature-based measure for flood risk reduction,we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure.In this perspective,we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence.We show that the forest properties that comprise coastal flood protection are well-known,but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation.Overall,there is relatively good understanding of the ecological processes that drive forest structure and size,but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics,and on the role of combined stressors influencing forest retreat.Integrating simulation models of forest structure under changing physical(e.g.due to sea-level change)and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection.
基金the Fundamental Research Funds for the Central Universities(NT2021026).
文摘A terahertz(THz)wave transmitted through vegetation experiences both absorption and scattering caused by the air molecules and leaves.This paper presents the scattering attenuation characteristics of vegetation in a THz range.The theoretical path loss model near the vegetation yields the average attenuation of THz waves in a mixed channel composed of air and vegetation leaves.Furthermore,a simplified model of the vegetation structure is obtained for generic vegetation types based on a variety of parameters,such as leaf size,distribution,and moisture content.Finally,based on specific vegetation species and different levels of air humidity,the attenuation characteristics under different conditions are calculated,and the influence of different model parameters on the attenuation characteristics is obtained.
文摘Recordings of seismic waves propagating from earthquake source to a station at the earth’s surface are a system response function. The convolution operator in time domain can be simplified as a multiplication operator in frequency domain. We discuss in frequency domain the separation of source, path and site effects for global scaling of earthquake source radiation. Also discussed are source scaling model, faulting mechanism, and the H/V inversion problems with crustal and near surface structures. Gross features of apparent source spectra appear to be not much region dependent although there may be difference between tectonic styles within a region of tectonic mixture for which we need further study as data accumulate. Vertical spectra may be a better approach to approximate source radiation, as it has less crustal amplification effects than horizontal spectra. The H/V ratio is evidently a comprehensive indicator of amplification effects from near surface to deep structure. This gives it potential as an inversion tool to deduce site crustal structure.
