Microseismic events enhancement and detection in sensor arrays using autocorrelation‐based filtering          下载免费PDF全文

Entao Liu  Lijun Zhu  Anupama Govinda Raj  James H. McClellan  Abdullatif Al‐Shuhail  SanLinn I. Kaka  Naveed Iqbal 《Geophysical Prospecting》2017,65(6):1496-1509

Passive microseismic data are commonly buried in noise, which presents a significant challenge for signal detection and recovery. For recordings from a surface sensor array where each trace contains a time‐delayed arrival from the event, we propose an autocorrelation‐based stacking method that designs a denoising filter from all the traces, as well as a multi‐channel detection scheme. This approach circumvents the issue of time aligning the traces prior to stacking because every trace's autocorrelation is centred at zero in the lag domain. The effect of white noise is concentrated near zero lag; thus, the filter design requires a predictable adjustment of the zero‐lag value. Truncation of the autocorrelation is employed to smooth the impulse response of the denoising filter. In order to extend the applicability of the algorithm, we also propose a noise prewhitening scheme that addresses cases with coloured noise. The simplicity and robustness of this method are validated with synthetic and real seismic traces.  相似文献   

A review of the LATEX project: mesoscale to submesoscale processes in a coastal environment   总被引：1，自引：1，他引：0  

Anne A. Petrenko  Andrea M. Doglioli  Francesco Nencioli  Marion Kersalé  Ziyuan Hu  Francesco d’Ovidio 《Ocean Dynamics》2017,67(3-4):513-533

The main objective of the LAgrangian Transport EXperiment (LATEX) project was to study the influence of coastal mesoscale and submesoscale physical processes on circulation dynamics, cross-shelf exchanges, and biogeochemistry in the western continental shelf of the Gulf of Lion, Northwestern Mediterranean Sea. LATEX was a five-year multidisciplinary project based on the combined analysis of numerical model simulations and multi-platform field experiments. The model component included a ten-year realistic 3D numerical simulation, with a 1 km horizontal resolution over the gulf, nested in a coarser 3 km resolution model. The in situ component involved four cruises, including a large-scale multidisciplinary campaign with two research vessels in 2010. This review concentrates on the physics results of LATEX, addressing three main subjects: (1) the investigation of the mesoscale to submesoscale processes. The eddies are elliptic, baroclinic, and anticyclonic; the strong thermal and saline front is density compensated. Their generation processes are studied; (2) the development of sampling strategies for their direct observations. LATEX has implemented an adaptive strategy Lagrangian tool, with a reference software available on the web, to perform offshore campaigns in a Lagrangian framework; (3) the quantification of horizontal mixing and cross-shelf exchanges. Lateral diffusivity coefficients, calculated in various ways including a novel technique, are in the range classically encountered for their associated scales. Cross-shelf fluxes have been calculated, after retrieving the near-inertial oscillation contribution. Further perspectives are discussed, especially for the ongoing challenge of studying submesoscale features remotely and from in situ data.  相似文献   

The choice of oil-pollution criteria for organogenic bottom sediments by chromatography-mass-spectrometry     

M. G. Kul’kov  E. A. Zarov  I. V. Filippov 《Water Resources》2017,44(2):267-275

The results of studying the hydrocarbon composition of organogenic bottom sediments of oil-polluted lakes and lakes of similar types remote from centers of anthropogenic activity are given. To correctly assess the oil pollution of organogenic materials one has to take into account the presence of native hydrocarbons in their composition and to choose the main criterion of oil pollution based on the presence of specific oil components not characteristic of aquatic ecosystems in their natural state. The most promising among such components are alkylbenzenes С₁₅–С₂₅, which slowly degrade under the conditions typical of northern aquatic ecosystems and can be retained for a long time by organogenic matrix.  相似文献   

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations     

Louise Nuijens  Kerry Emanuel  Hirohiko Masunaga  Tristan L’Ecuyer 《Surveys in Geophysics》2017,38(6):1257-1282

Space-borne observations reveal that 20–40% of marine convective clouds below the freezing level produce rain. In this paper we speculate what the prevalence of warm rain might imply for convection and large-scale circulations over tropical oceans. We present results using a two-column radiative–convective model of hydrostatic, nonlinear flow on a non-rotating sphere, with parameterized convection and radiation, and review ongoing efforts in high-resolution modeling and observations of warm rain. The model experiments investigate the response of convection and circulation to sea surface temperature (SST) gradients between the columns and to changes in a parameter that controls the conversion of cloud condensate to rain. Convection over the cold ocean collapses to a shallow mode with tops near 850 hPa, but a congestus mode with tops near 600 hPa can develop at small SST differences when warm rain formation is more efficient. Here, interactive radiation and the response of the circulation are crucial: along with congestus a deeper moist layer develops, which leads to less low-level radiative cooling, a smaller buoyancy gradient between the columns, and therefore a weaker circulation and less subsidence over the cold ocean. The congestus mode is accompanied with more surface precipitation in the subsiding column and less surface precipitation in the deep convecting column. For the shallow mode over colder oceans, circulations also weaken with more efficient warm rain formation, but only marginally. Here, more warm rain reduces convective tops and the boundary layer depth—similar to Large-Eddy Simulation (LES) studies—which reduces the integrated buoyancy gradient. Elucidating the impact of warm rain can benefit from large-domain high-resolution simulations and observations. Parameterizations of warm rain may be constrained through collocated cloud and rain profiling from ground, and concurrent changes in convection and rain in subsiding and convecting branches of circulations may be revealed from a collocation of space-borne sensors, including the Global Precipitation Measurement (GPM) and upcoming Aeolus missions.  相似文献   

Paleomagnetism of the Upper Paleozoic of the Novaya Zemlya Archipelago     

V. V. Abashev  D. V. Metelkin  N. E. Mikhal’tsov  V. A. Vernikovsky  N. Yu. Matushkin 《Izvestiya Physics of the Solid Earth》2017,53(5):677-694

The rock magnetic and paleomagnetic results from the Upper Paleozoic sedimentary sequences composing the isles of the Novaya Zemlya Archipelago are presented. The recorded temperature dependences of the magnetic susceptibility, the magnetic hysteresis parameters, and the results of the first-order reversal curve (FORC) measurements suggest the presence of single-domain or pseudo-single-domain magnetite and hematite grains in the rocks. The Upper Paleozoic deposits overall are promising for unraveling the tectonic evolution of the Barents–Kara region. Together with the rock magnetic data, the positive fold and reversal tests testify to the primary origin of the indentified magnetization components. However, the interpretation of the paleomagnetic data should take into account the probable inclination shallowing. New substantiation is offered for the paleomagnetic poles for Early Devonian and Late Permian. For the first time, paleomagnetic constraints are obtained for the Late Carboniferous boundary. It is shown that the Early Cimmerian deformation stage within the Paikhoi–Novaya Zemlya region is associated with the sinistral strike slip displacement along the Baidaratskii suture during which the internal structure of the Southern Novaya Zemlya segment could undergo shear in addition to the nappe-thrust transformations. The Northern Novaya Zemlya segment, which is shifted northwest with respect to the Southern segment, was deformed in the thrusting mode with an overall clockwise rotation of this segment relative to the East European Craton.  相似文献   

New data on the Late Cenozoic basaltic volcanism in Syria,applied to its origin     

V.G. Trifonov  A.E. Dodonov  E.V. Sharkov  D.I. Golovin  I.V. Chernyshev  V.A. Lebedev  T.P. Ivanova  D.M. Bachmanov  M. Rukieh  O. Ammar  H. Minini  A.-M. Al Kafri  O. Ali 《Journal of Volcanology and Geothermal Research》2011,199(3-4):177-192

New data on geology and 21 K–Ar dates of the Late Oligocene–Quaternary basalts in Syria, combined with analysis of the new and previous data are used to reconstruct the volcanic history and relations between it and tectonic events. Volcanism began at the end of Oligocene (26–24 Ma) and was concentrated in the Late Oligocene–Early Miocene along a N-trending band, which stretches from the Jebel Arab (Harrat Ash Shaam) up to Kurd Dagh and southern Turkey. Activity waned in the Middle Miocene (17–12 Ma), but was resumed in the same band in the Tortonian and increased in the Messinian and Early Pliocene (6.3–4 Ma), when volcanism spread to the Shin Plateau and its coastal extension. After a brief hiatus ～ 4–3.5 Ma, volcanism became still more intensive and spread from the N-trending band to the east into the northern margin of the Mesopotamian Foredeep and to the west into the Dead Sea Transform zone. Additional eruptions continued into the Holocene.Volcanism lasted > 25 million years in the Jebel Arab Highland and > 15 million years in the Aleppo Plateau. The long duration of volcanism in the same parts of the moving Arabian plate and absence of records of one-way migration of the activity mean that the magmatic sources moved together with the plate, i.e., they were situated within the lithosphere mantle. Coincidence of the tectonic and volcanic stages of the Arabian plate development proves that volcanic activity depended on the geodynamic situation, caused by the plate motion. Situated within the lithosphere, magmatic sources within this transverse band were possibly caused by thermal and deforming influences of the asthenospheric lateral flow, moved laterally from the Ethiopia–Afar deep superplume.  相似文献   

Insights on the events surrounding the final drainage of Lake Ojibway based on James Bay stratigraphic sequences     

M. Roy  F. Dell’Oste  J.J. Veillette  A. de Vernal  J.-F. Hélie  M. Parent 《Quaternary Science Reviews》2011,30(5-6):682-692

Deglaciation of the James Bay region was highly dynamic, with the occurrence of ice (Cochrane) readvances into glacial Lake Ojibway around final deglaciation time, which culminated with the drainage of Ojibway waters into Hudson Bay and subsequent incursion of the Tyrrell Sea at ～8 ka. Renewed interest on these events comes from the possible link between the drainage of the ice-dammed Lake Agassiz-Ojibway and a major climate deterioration known as the 8.2-ka cooling event. Recent glaciological modeling suggests that this drainage may have occurred subglacially, a mechanism that can accommodate more than one lake discharge, as suggested by marine records. The exact number and timing of drainage events, as well as location of the lake discharge pathway(s) remain, however, largely unconstrained. Here we focus on the events that led to the drainage of Lake Ojibway by documenting late-glacial sedimentary sequences located east of James Bay. Our investigations indicate that the deglacial sequence consists of a readvance till, extensive Ojibway rhythmites, and thick marine sediments. The glaciolacustrine and marine units are separated by a 60 cm-thick horizon composed of laminated silt beds containing rounded clay balls and disseminated clasts resulting from the abrupt drainage of the lake. Radiocarbon dating of marine fossils lying above the drainage horizon indicates that the glaciolacustrine episode ended around 8128–8282 cal yr BP. Micropaleontological analyses reveal that freshwater ostracods (Candona sp.) and marine microfossils (foraminifers, dinocysts) occur together in the upper part of the Ojibway sediments. Analysis of oxygen isotopes (δ¹⁸O) of ostracods and foraminifers originating from the same stratigraphic position show highly contrasting values that suggest possible subglacial exchanges between Lake Ojibway and Tyrrell Sea waters prior to the final drainage event. The complexity of the deglacial events is further indicated by radiocarbon dating of marine shells retrieved from a Cochrane till that suggests that the last ice readvance occurred almost simultaneously with the final lake discharge. These results bring additional constraints on the drainage mechanism of the coalesced Lake Agassiz-Ojibway and indicate that the James Bay region formed an important drainage pathway for meltwaters at the end of the last deglaciation.  相似文献   

Thermal anomalies on Savich Cone,Kikhpinych Volcano,Kamchatka: IR surveys and land-based observations for 30 years (1982 through 2012)     

O. F. Kardanova  I. K. Dubrovskaya  Ya. D. Murav’ev 《Journal of Volcanology and Seismology》2015,9(6):368-377

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Field Simulation of Cadmium Pollution of a Freshwater Body     

D. N. Gar’kusha  Yu. A. Fedorov  T. V. Knyazeva  N. S. Tambieva 《Water Resources》2018,45(5):746-756

An experiment in mesocosms installed in a fish-rearing pond was used to adequately simulate the character of self-purification, migration, and the redistribution of cadmium and its chemical forms in major components of a freshwater ecosystem, into which this chemical is imported in concentrations far in excess of its MAC. The major portion of the imported cadmium was found to be removed from the water mass within a few days, mostly, as a component of particulate matter settling onto the bed, including dead plankton remains, as ion-exchange cadmium forms adsorbed by suspension (37%), and as forms associated with ferromanganese oxides (41%). The rate of cadmium removal from the water mass is determined both by the amount of particulate matter settling onto the bed and the efficiency of cadmium sorption by it, depending on the acid–alkaline and redox conditions in the water body.  相似文献   

基于OLCI数据的洱海叶绿素a浓度估算     

毕顺  李云梅  吕恒  朱利  牟蒙  雷少华  徐杰  温爽  丁潇蕾 《湖泊科学》2018,30(3):701-712

海陆颜色仪(OLCI)是搭载在Sentinel-3上的新型水色遥感传感器,其对于内陆清洁水体水质遥感监测的适用性有待验证.本研究以评价水体富营养化程度的重要参数叶绿素a(Chl.a)浓度为指标,以高原湖泊洱海为研究区,基于2017年4月19日共20个星地同步实验数据,建立了3种可应用于OLCI数据的Chl.a浓度遥感估算模型(波段比值模型、三波段模型以及FLH模型),并估算了当日洱海Chl.a浓度的空间分布.结果表明:(1)选用波段Oa8(665 nm)、Oa11(708.75 nm)和Oa12(753.75 nm)构建的三波段模型最适用于洱海水域的Chl.a浓度估算,其平均绝对误差百分比为12.37%,低于波段比值模型的16.04%和FLH模型的13.50%;(2)对OLCI使用的大气校正方法中,基于去瑞利散射的暗像元法对估算模型的适用性要优于6S、FLAASH以及QUAC方法;(3)洱海OLCI影像中近岸水体受邻近效应影响严重,近红外波段Oa12(753.75 nm)受陆地邻近效应影响的距离为1~2个像元,而Oa8(665 nm)、Oa10(681.25 nm)和Oa11(708.75 nm)波段为1个像元;(4)2017年4月19日全湖Chl.a浓度均值为12.15±5.72μg/L,洱海中部水域Chl.a浓度最低(9.00~12.00μg/L),北部水域浓度最高(12.00~22.76μg/L),南部水域浓度稍高(12.00~14.00μg/L),阳南溪与波罗江入湖口受降雨径流的影响出现"羽流现象",导致Chl.a浓度偏低,约为8.33μg/L.  相似文献