Reverse time migration of CMP-gathers an effective tool for the determination of interval velocities     

Dan Loewenthal  Theodor Krey 《Surveys in Geophysics》1989,10(2-4):349-376

One of the most important steps in the conventional processing of reflection seismic data is common midpoint (CMP) stacking. However, this step has considerable deficiencies. For instance the reflection or diffraction time curves used for normal moveout corrections must be hyperbolae. Furthermore, undesirable frequency changes by stretching are produced on account of the dependence of the normal moveout corrections on reflection times. Still other drawbacks of conventional CMP stacking could be listed.One possibility to avoid these disadvantages is to replace conventional CMP stacking by a process of migration to be discussed in this paper. For this purpose the Sherwood-Loewenthal model of the exploding reflector has to be extended to an exploding point model with symmetry to the lineP _EX M whereP _EX is the exploding point, alias common reflection point, andM the common midpoint of receiver and source pairs.Kirchhoff summation is that kind of migration which is practically identical with conventional CMP stacking with the exception that Kirchhoff summation provides more than one resulting trace.In this paper reverse time migration (RTM) was adopted as a tool to replace conventional CMP stacking. This method has the merit that it uses the full wave equation and that a direct depth migration is obtained, the velocityv can be any function of the local coordinatesx, y, z. Since the quality of the reverse time migration is highly dependent on the correct choice of interval velocities such interval velocities can be determined stepwise from layer to layer, and there is no need to compute interval velocities from normal moveout velocities by sophisticated mathematics or time consuming modelling. It will be shown that curve velocity interfaces do not impair the correct determination of interval velocities and that more precise velocity values are obtained by avoiding or restricting muting due to non-hyperbolic normal moveout curves.Finally it is discussed how in the case of complicated structures the reverse time migration of CMP gathers can be modified in such a manner that the combination of all reverse time migrated CMP gathers yields a correct depth migrated section. This presupposes, however, a preliminary data processing and interpretation.  相似文献   

Mitteilungen     

Theodor Stocks 《Ocean Dynamics》1955,8(3):128-128

Ohne Zusammenfassung  相似文献   

Seeing Conditions at Sutherland. Results of the 1992/93 seeing campaign     

Josef Gochermann  Walter F. Wargau  Claus Tappert  Theodor Schmidt-Kaler  Robert S. Stobie  Fred Marang  Greg Roberts  Francois G. van Wyk  Peter Rucks 《Experimental Astronomy》1999,9(1):1-15

In order to decide whether the seeing conditions at SAAO/Sutherland justify the erection of a 3.5 m telescope and also to compare Sutherland with the Gamsberg/Namibia site, a seeing campaign covering 15 months has been carried out. For direct comparison with the results of the seeing campaign at Gamsberg twenty years before the same QUESTAR telescope was employed. The seeing is determined by the scattering of the star-trail exposed on a film in the focal plane of the telescope. The campaign commenced in February 1992. Up to May 1993, data for 204 nights, that is 47.3% of the total number of nights, were collected. Due to wind speeds above 30 km h^-1, 25 out of the 204 nights were not considered in the final reduction. The useful 179 nights are evenly distributed over the campaign period. The median seeing value for the whole period is = 0.52. There are differences during the year: the best season gives = 0.42, the worst = 0.67. Each night was divided into three intervals, although data for each of the three intervals were not always available. Generally, there is an improvement in the seeing during the course of a night. The results are compared to the seeing values of Gamsberg/Namibia and ESO/La Silla.  相似文献   

The Pindos Fold-and-thrust belt (Greece): inversion kinematics of a passive continental margin   总被引：1，自引：0，他引：1  

Konstantinos?Skourlis  Theodor?DoutsosEmail author 《International Journal of Earth Sciences》2003,92(6):891-903

Continuous exposure in the Pindos mountain chain (Greece) and the detailed stratigraphic measurements in the area enable us to construct eight balanced cross sections across the Pindos Fold-and-thrust belt (PFTB) and to approach quantitatively some parameters which controlled foreland evolution. The 160-km-wide passive continental margin of the Apulian continent in Greece was progressively shortened from east to west at rates of 6 mm/year between the Early Oligocene and Late Eocene. From the rear to the frontal part of the wedge, fault-bend folds, duplexes and imbricates were formed, while strain was partitioned into faulting (~34%), layer parallel shortening (~23%) and buckling (~9%). Foreland subsidence and internal deformation of the orogenic wedge are strongly affected by two parameters of equal importance: the thrust load of the overthrusted microcontinents and the rigidity of the underthrusted Apulian passive margin. Changes in the thickness of the pre-orogenic sediments and reactivated transform faults induced salients. During the Lower Miocene, the orogenic wedge in the Peloponnese suffered additional uplift and westward gravitational gliding induced by the intracontinental subduction of the Palaeozoic rift zone of the Phyllite-Quartzite Series, which was reactivated and returned to the earths surface during the Hellenic orogeny.  相似文献   

Geologic evolution of the westernmost part of the internal Betic zone (Betic Cordilleras,Southern Spain)     

Dr. Theodor Ernst Felder 《International Journal of Earth Sciences》1980,69(1):131-148

The Serranía de Ronda (western Betic Cordilleras, S-Spain) is formed by different tectonic units of the Betic internal domain. Stratigraphic correlations of the Permo-Triassic and Triassic sedimentary sequences imply that one part of the Mesozoic carbonates of the Rondaides (Dorsale bétique), namely the Cabrilla unit (Dorsale interne), is shearedoff from the frontal part of the Malaguides, and another part (Nieves unit, Dorsale externe) forms the Mesozoic cover of the alpujarride Casares unit. The first alpine compressional phases took place in the Paleogene; post-metamorphic movements followed in the time between the Upper Aquitanian and the Upper Tortonian. From geometrical considerations it can be concluded that the Malaguides originated paleogeographically from a more internal region than the Alpujarrides.

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Zusammenfassung Am Aufbau der Serranía de Ronda (westliche Betische Kordilleren, S-Spanien) nehmen verschiedene Einheiten der betischen Intemzonen teil. Stratigraphische Vergleiche der permotriadischen und triadischen Sedimentserien erlauben den Schluß, daß die mesozoischen Karbonate der Rondaiden (Dorsale bétique) zu einem Teil (Cabrilla-Einheit, Dorsale interne) von der frontalen Partie der Malagiden abglitten und zum anderen Teil (Nieves-Einheit, Dorsale externe) das abgescherte Mesozoikum der alpujarriden Casares-Einheit bilden. Die ersten alpinen Kompressionsphasen sind im Paleogen anzusetzen, da für mesozoische Deckenbewegungen beweiskräftige Argumente fehlen. Zwischen Oberaquitanian und Obertortonian fanden post-metamorphe Überschiebungen statt. Aus geometrischen Gründen wird angenommen, daß die Malagiden paläogeographisch internerer Herkunft sein müssen als die benachbarten Alpujarriden.

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Resumen La Serranía de Ronda (Cordilleras béticas occidentales, Prov. Málaga) está formado por diferentes unidades del conjunto bético interno. Correlaciones estratigráficas del Permo-Triásico y del Triásico de los diferentes unidades permiten la conclusión que los Rondáides (Dorsal bética) está por una parte (unidad de Cabrilla, Dorsal interna) el revestimiento mesozóico de la parte frontal de los mantos maláguides, y por otra parte (unidad de las Nievas, Dorsal externa) la parte mesozóica de la unidad alpujárride de Casares. Las primeras fases alpinas de compresión deben ser situadas en el Paleógeno. Las traslaciones post-metamórficas de mantos son de edad aquitaniense superior hasta pre-tortoniense superior. Con argumentación geométrica se puede concluir que los Maláguides son de un orígen paleográfico más interno que los Alpujárrides.

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( , . « » , (Dorsale bétique) ( , Dorsale interne) , ( , Dorsale externe) . .. , . - . , , .

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Der Boden der südlichen Nordsee     

Theodor Stocks 《Ocean Dynamics》1956,9(6):265-280

Zusammenfassung In Gezeitengebieten wie dem vorliegenden (südliche Nordsee, wofür eine Neubearbeitung vorgelegt wird) wurde bisher meistens das den Seekarten und anderen Quellen entstammende Zahlenmaterial ohne weitere Beschickung als Grundlage für die Bearbeitung von Tiefenkarten verwendet.Dabei wurde und wird das Seekartennull meistens stillschweigend als Kartennull für Isobathenkarten mit übernommen, obwohl sich manche Bearbeiter der Fehlerhaftigkeit dieser Annahme wohl bewußt gewesen sein mögen. Besonders unangenehm macht sich diese Tatsache bemerkbar, wenn Isobathen des Seegebietes mit Isohypsen im Watt oder auf dem festen Lande und auf Inseln in Verbindung gebracht werden sollen.Die jetzt vorgelegte Tiefenkarte versucht, dieses Dilemma durch Berücksichtigung einer für das ganze Gebiet gültigen, also von dem örtlich verschiedenen Seekartennull unabhängigen Niveaufläche zu umgehen; es wird eine Methode angegeben, die im Gebiet der südlichen Nordsee angewandt wurde, und im Hinblick auf die Isobathenäquidistanz (10 m im Ergebnis, 5 m im Entwurf) kritisch auf die möglichen Fehler untersucht. Es wird ferner, erläutert an einem konkreten Beispiel, auf den Unterschied zwischen den Seekarten-Tiefenlinien (nautischen Warnlinien) und echten morphologischen Isobathen hingewiesen; allerdings ist ein Anschluß der so gewonnenen Niveaufläche für die Tiefen der südlichen Nordsee an die beiderseitigen Landeshorizonte noch nicht möglich.

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A new bathymetric chart of the Southern North Sea

Summary For charts of tidal regions like that of the Southern North Sea, for which a revised edition is herewith presented, the numerical values required as basic elements for the construction of bathymetric charts have until now mostly been taken — without foregoing correction — from existing charts and other sources. Besides, in most cases, chart datum has been and still is continued to be used as ordnance datum for the construction of contour lines, though many a chart author may have been well aware of the uncorrectness of this procedure. The deficiency makes itself felt in a most disagreeable way when isobaths of the sea regions are to be combined with isohypses of regions of tidal flats or connected to such of the continent or of islands.The bathymetric chart herewith presented tries to avoid this uncorrectness by using a reference plane valid for all types of regions and, hence, independent of chart datum which is subject to local differences in height. The method that has been used for constructing the chart of the Southern North Sea is discussed and carefully scrutinized for any errors that may possibly occur with regard to the equidistance of isobaths (in this case 10 m on fair charts, 5 m on plotting charts). In addition, by way of practical example, attention is called to the difference existing between depth contours on charts (nautical danger lines) and true morphologic isobaths. It is, however, not yet possible to connect the new reference plane on which the depth contours on the new bathymetric chart of the Southern North Sea have been based to the ordnance datum used in mapping the countries adjoining the area covered by the new chart.

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Une nouvelle carte bathymétrique de la partie sud de la mer du Nord

Résumé Pour l'établissement des cartes bathymétriques représentant des zones soumises à la marée comme celle de la partie sud de la mer du Nord, on s'est jusqu'ici servi des valeurs numériqúes provenant des cartes marines et d'autres sources, sans avoir corrigé ces valeurs avant leur usage. En outre, on a employé le plus souvent, et on continue encore à employer le «zéro hydrographique» comme «zéro du nivellement général» pour la construction de lignes de niveau bienque beaucoup d'auteurs de cartes se soient, sans doute, rendu compte de l'inexactitude de cette méthode. Cette défectuosit é présente des inconvénients extraordinaires lorsque des isobathes de la région marine sont à com biner avec des isohypses de zones couvrantes et découvrantes ou à relier à celles du continent.Par rapport à l'édition refondue de la carte bathymétrique présentée avec ce travail et représentant la zone soumise à la marée de la région sud de la mer du Nord, on a essayé d'éviter cette inexactitude par l'introduction d'un nouveau plan de référence qui est valable pour des régions de caractères bien différents, et qui ne dépend pas du zéro hydrographique soumis à des différences locales en hauteur. La méthode qui fut appliquée à l'établissement de cette carte est discutée dans ce travail et examinée avec soin pour éviter que des erreurs pourraient s'introduire dans des équidistances des isobathes (dans ce cas, 10 m sur les minutes de rédaction, 5 m sur les minutes de construction). En outre, un exemple pratique sert à attirer l'attention sur la différence entre des lignes de niveau (limites de danger) indiquées sur des cartes marines et des isobathes vraiment morphologiques. Cependant, il n'est pas encore possible de relier le nouveau plan de référence sur lequel s'appuient les lignes de niveau de la nouvelle carte bathymétrique, au zéro du nivellement général en usage pour la représentation topographique des pays contigues à la région couverte par cette carte.

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Die Karte kann auch einzeln zum Preis von DM 3,- je Stück durch den Buchhandel oder unmittelbar vom D.H.I. bezogen werden (Druckschrift Nr. 2560 des D.H.I.).  相似文献   

Volatile organic compounds in open ocean and coastal surface waters     

Theodor C. Sauer 《Organic Geochemistry》1981,3(3):91-101

Volatile organic compounds with volatilities ranging between those of n-hexane and n-pentadecane were identified in open ocean and coastal marine surface water samples taken in the north central part of the Gulf of Mexico. Approximately 40 organic compounds were found. The types and concentrations of the compounds found depended upon the extent of anthropogenic and terrestrial influences. Open ocean samples consisted mostly of aromatic hydrocarbons, whereas coastal samples included alkanes, cycloalkanes, cycloalkenes, aromatic hydrocarbons, aldehydes and chlorinated hydrocarbons. Unpolluted open ocean and coastal water samples had individual concentrations rarely exceeding 5 ng/kg; some aromatic hydrocarbons approached 15 ng/kg. n-Pentadecane dominated the hydrocarbons in these samples (50–100 ng/kg). The most polluted coastal water samples had individual volatile organic concentrations as great as 150 ng/kg with total concentrations approaching 1000 ng/kg. The terpene, limonene, was found extensively in the coastal samples (up to 40 ng/kg). Photooxidization of hydrocarbons in industrial/urban atmospheres was considered as a possible source of aldehydes present in coastal water. The dynamic headspace stripping/Tenax-GC adsorption method coupled with packed column gas chromatography, and gas chromatography-mass spectrometry were used for volatile organic analysis.  相似文献   

V475 Sct (Nova Scuti 2003) – Binary or Triple System?     

Drahomír Chochol  Theodor Pribulla  Nataly A. Katysheva  Sergei Yu. Shugarov  Igor M. Volkov 《Astrophysics and Space Science》2005,296(1-4):135-139

UBV RI photometry and 4600–9000 Å spectroscopy of nova V475 Sct taken in the first 3 month after discovery is presented. The object can be classified as a Fe II type slow nova with t _2,V = 48 days, t _3,V = 53 days. The absolute magnitude of the nova at maximum, its colour excess and distance were determined. The observed 13.4 day periodicity of flares can be explained by the mass transfer bursts from the red to the white dwarf, probably caused by the periastron passage of a third body. Two sets of absorptions are seen in the P Cyg-type Hα line profile. They arise in the expanding shell of the nova.  相似文献   

Ccd Photometry of the Neglected Contact Binaries V344 Lac and V1191 Cyg     

Theodor Pribulla  Martin Vaňko  DrahomÍr Chochol  Štefan Parimucha  Daniel Baluďanský 《Astrophysics and Space Science》2005,296(1-4):281-284

New photoelectric and CCD observations of the eclipsing contact binary systems V344 Lac and V1191 Cyg are presented and analyzed. All available times of minimum light were used to study period changes of the systems and determine up-to-date ephemerides. The orbital period of V1191 Cyg is found to be increasing at a very fast rate. The photometric elements were determined using the new light curve, radial-velocity curve and broadening function fitting code ROCHE.  相似文献   

The Corinth-Patras rift as the initial stage of continental fragmentation behind an active island arc (Greece)   总被引：1，自引：0，他引：1  

THEODOR Doutsos  NIKOLAOS Kontopoulos  GEORGIOS Poulimenos 《Basin Research》1988,1(3):177-190

Abstract During the migration of the back arc extension from central to western Greece the Corinth and Patras grabens are being formed. Orthogonal opening of these graben zones is accomplished by WNW listric normal faults and NNE transfer faults which produce an along-axis fragmentation. The listric faults show an increase in the dip of the fault plane westwards as well as a decrease in the maximum extension rate from 50% to the east in the Corinth graben, to 10% to the west in the Patras graben. Similarly, towards the west, Plio-Quaternary deposits become thinner whereas Pliocene sediments thin-out indicating a westward rift propagation.
As the back arc extension migrates westwards it is interacting or is being superimposed above another orthogonal fault system consisting of NNW and ENE normal faults. These faults have been formed during general uplift behind the orogenic front which has been migrating from western Greece to the Ionian islands. The ENE-trending Rio graben which belongs to his orthogonal system connects the Patras graben to the Corinth graben and has subsequently been active as a transfer fault between them.
Plio-Quaternary geodynamic processes in central continental Greece are quite similar to those earlier processes observed in the central Aegean region which reflect the initial stage of continental break-up behind a migrating orogenic front.  相似文献