GIS中几何对象之间的空间关系

几何对象之间的空间关系是GIS研究的重要理论问题之一，在分析ArcInfo和OpenGIS对空间关系描述的基础上，运用基于维数扩展的9交模型，得到在实际应用中基本的空间关系分类，并对空间关系的进一步研究提出了展望。     

Opening geometry of the Kurile Basin (Okhotsk Sea) as inferred from structural data

Abstract   The Kurile Basin in the Okhotsk Sea, northwestern Pacific, is a back-arc basin located behind the Kurile Island Arc. It is underlain by oceanic crust and its origin has been attributed to back-arc spreading. Two models for the opening of the Kurile Basin exist, for which the spreading axis is oriented northeast–southwest and northwest–southeast, respectively. New data are presented here on the morphostructure of the slope of the northern Kurile Basin and of the central Kurile Basin which support a strike of the spreading axis in the latter direction. Bathymetric as well as single-channel and multichannel seismic reflection data demonstrate the existence of dominant northwest-striking normal faults on the northern slope of the Kurile Basin. In the central Kurile Basin a basement rise striking north-northwest–south-southeast (here named the Sakura Rise) was mapped. The rise morphology has the distinct imprint of a rift structure with symmetrical volcanic edifices on the rise axis and faulted blocks that tilt in opposite directions on the flanks. These data suggest that the Kurile Basin opened in a northeast–southwest direction. In the generally accepted plate tectonic reconstructions, northwest–southeast spreading associated with dextral strike–slip along the north–south-striking shear zone of Sakhalin and Hokkaido islands has been assumed. In the present model, spreading in the Kurile Basin was presumably connected with dextral displacement along a northeast-striking shear zone on the southern segment of the Okhotsk Sea.     

A note on the effects of nonuniform spreading velocity of submarine slumps and slides on the near-field tsunami amplitudes

The effects of variable speeds of spreading of submarine slides and slumps on near-field tsunami amplitudes are illustrated. It is shown that kinematic models of submarine slides and slumps must consider time variations in the spreading velocities, when these velocities are less than about 2c_T, where is the long period tsunami velocity in ocean of constant depth h. For average spreading velocities greater than 2c_T, kinematic models with assumed constant spreading velocities provide good approximation for the tsunami amplitudes above the source.     

Revised tectonic implications for the magnetic anomalies of the western Weddell Sea

Ten years after the USAC (U.S.–Argentina–Chile) Project, which was the most comprehensive aeromagnetic effort in the Antarctic Peninsula and surrounding ocean basins, questions remain regarding the kinematics of the early opening history of the Weddell Sea. Key elements in this complex issue are a better resolution of the magnetic sequence in the western part of the Weddell Sea and merging the USAC data set with the other magnetic data sets in the region. For this purpose we reprocessed the USAC data set using a continuation between arbitrary surfaces and equivalent magnetic sources. The equivalent sources are located at a smooth crustal surface derived from the existing bathymetry/topography and depths estimated by magnetic inversions. The most critical area processed was the transition between the high altitude survey over the Antarctic Peninsula and the low altitude survey over the Weddell Sea that required downward continuation to equalize the distance to the magnetic source. This procedure was performed with eigenvalue analysis to stabilize the equivalent magnetic source inversion.The enhancement of the Mesozoic sequence permits refining the interpretation of the seafloor-spreading anomalies. In particular, the change in shape and wavelength of an elongated positive in the central Weddell Sea suggests that it was formed during the Cretaceous Normal Polarity Interval. The older lineations in the southwestern Weddell Sea are tentatively attributed to susceptibility contrasts modeled as fracture zones. Numerical experimentation to adjust synthetic isochrons to seafloor-spreading lineations and flow lines to fracture zones yields stage poles for the opening of the Weddell Sea since 160 Ma to anomaly 34 time. The corresponding reconstructions look reasonable within the known constraints for the motions of the Antarctic and South America plates. However, closure is not attained between 160 and 118 Ma if independent published East Antarctica–Africa–South America rotations are considered. The lack of closure may be overcome by considering relative motion between the Antarctic Peninsula and East Antarctica until 118 Ma time, an important component of convergence.     

Vertical extrusion and middle crustal spreading of omphacite granulite: a model of syn-convergent exhumation (Bohemian Massif, Czech Republic)

The exhumation of eclogite facies granulites (Omp–Plg–Grt–Qtz–Rt) in the Rychleby Mts, eastern Czech Republic, was a localised process initiated by buckling of crustal layers in a thickened orogenic root. Folding and post‐buckle flattening was followed by the main stage of exhumation that is characterized by vertical ductile extrusion. This process is documented by structural data, and the vertical ascent of rocks from a depth of c. 70 to c. 35 km is documented by metamorphic petrology. SHRIMP ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²⁰⁶Pb evaporation zircon ages of 342 ± 5 and 341.4 ± 0.7 Ma date peak metamorphic conditions. The next stage of exhumation was associated with sideways flat thrusting associated with lateral viscous spreading of granulites and surrounding rocks over indenting adjacent continental crust at a depth of c. 35–30 km. This stage was associated with syntectonic intrusion of a granodiorite sill at 345–339 Ma, emplaced at a crustal depth of c. 25 km. The time required for cooling of the sill as well as for heating of the country rocks brackets this event to a maximum of 250 000 years. Therefore, similar ages of crystallization for the granodiorite magma and the peak of eclogite facies metamorphism of the granulite suggest a very short period of exhumation, limited by the analytical errors of the dating methods. Our calculations suggest that the initial exhumation rate during vertical extrusion was 3–15 mm yr^?1, followed by an exhumation rate of 24–40 mm yr^?1 during further uplift along a magma‐lubricated shear zone. The extrusion stage of exhumation was associated with a high cooling rate, which decreased during the stage of lateral spreading.     

The Break-up of a Long-term Relationship: the Cretaceous Separation of New Zealand from Gondwana

After a prolonged period of convergent margin tectonics in the Late Paleozoic and Mesozoic, resulting in terrane accretion, uplift and erosion of the New Zealand segment of Gondwana, the region saw a rapid change to extensional tectonics in mid-Cretaceous times. The change in regime is commonly marked by a major angular unconformity that separates the older, often strongly-deformed subduction-related ‘basement’ rocks from the younger, less-deformed ‘cover’ strata. The youngest ‘basement’ strata locally contain Albian fossils, and the youngest associated zircons have been radiometrically dated at ca. 100 Ma. In general the oldest strata overlying the unconformity contain fossils of similar Albian age, and the oldest radiometric dates also give similar dates of ca. 100 Ma, indicating a very rapid transition between the two tectonic regimes.The onset of extension resulted in the widespread development of grabens and half grabens, associated in the northwest of the South Island with a metamorphic core complex. In the west and south, on the thicker and more buoyant crust of most of the South Island, the new basins were infilled with mainly non-marine deposits. Non-marine graben infill consists of locally-derived breccia deposited as talus or debris flows on alluvial fans, passing directly as fan deltas or via fluvial deposits into lacustrine deposits. Active faulting continued in some areas until the initiation of sea floor spreading in Santonian times. Post-subduction strata on the thinner continental crust of the northeastern South Island and eastern North Island (East Coast Basin) were mainly marine. Initial sedimentary deposits in the west of the basin, reflecting extensional tectonism, consist of coarse-grained debris-flow deposits or olistostromes, generally fining upwards as tectonic activity waned: those in the east, including allochthonous sediments derived from the northeast, are dominated by turbidites. Early Cenomanian (ca. 96–98 Ma) injection of intraplate alkaline igneous rocks in central New Zealand caused updoming, resulting in shallowing and local uplift of the basin floor above sea level. A long (ca. 10 Ma) period of slow subsidence and transgressive marine sedimentation interrupted by episodic relative sea level changes followed.This pattern changed in the Late Coniacian (ca. 87–86 Ma), with a sudden influx of coarse, transgressive sands in eastern New Zealand. This was immediately preceded in parts of the region by uplift and erosion, probably driven by convective upwelling of the mantle just prior to sea-floor spreading, resulting in a ‘break-up’ unconformity. In the Late Santonian (ca. 85–84 Ma), development of a new, diachronous, widespread low-relief erosion surface, overlain by fine-grained deposits accompanying a rapid rise in relative sea level, coincided with the beginning of sea-floor spreading, rapid passive margin subsidence, and final separation of New Zealand from Gondwana.     

Systematic GIS-based landslide inventory as the first step for effective landslide-hazard management

The purpose of the so-called IFFI project (Inventario dei Fenomeni Franosi in Italia—Inventory of Landslides in Italy) and of many other related activities carried out by the Centro Regionale per le Ricerche Territoriali e Geologiche of ARPA Piemonte (Agenzia Regionale per la Protezione Ambientale—Regional Agency for Environmental Protection), is to map all the existing landslides in Piemonte (including both results of monitoring data and available historical data). ARPA carried out new systematic surveys using airphoto interpretation and created a specific alphanumeric geological information systems (GIS)-based database to store and process all the collected data. In order to obtain proper landslide-hazard zoning, it is necessary to provide a landslide inventory and to define the relationship between landslides and geological setting. A landslide inventory represents a fundamental base of knowledge, is a very basic tool for land planning, and strongly helps the local authorities in their decision making.     

Geomorphology and geochronology of sackung features (uphill-facing scarps) in the Central Spanish Pyrenees

The paper analyses uphill-facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central Spanish Pyrenees. Previous studies of sackung landforms in the Pyrenees have argued for deglacial unloading as the genetic mechanism, but this causal and temporal relationship has not been proved due to the lack of chronological data. The antislope scarps in the two studied locations, Vallibierna and Estós, are developed in Palaeozoic metasedimentary rocks (parallel to the contour lines and the structural grain), occur in the intermediate sector of the hillslope, and are up to 0.5 km long and several meters high. A trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis. Charcoal from the lowermost unit in Vallibierna provided an age of 5.9 cal. ka for the sackung and extrapolation of the three dates obtained in Estós indicates that the trough formed ca. 7.6–7.8 cal. ka. Deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka. The time lag of >5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development, but did not initiate the movement. Seismic shaking is proposed as a probable triggering factor. This hypothesis, although supported by the sudden deformation event recorded by a failure plane exposed in Vallibierna trench, and by the seismic and neotectonic activity of the area, cannot be proved due to the lack of chronological information about paleoearthquakes.