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Current research3D geologic map of Silicon Valley
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A new way of looking at Silicon ValleyWhat is the real 3-D geologic map?The block diagrams of the Santa Clara Valley 3D geologic map shown in the About the map and What information goes into the map? sections are not the actual geologic map, but are simply graphical representations extracted from the digital database that contains the complete map information. The real 3D geologic map, although not yet complete, exists within the computer as a complex, highly organized set of digital files and instructions. The 3D geologic map is framed around the earthVision® geologic modeling and visualization software and retains the fundamental architecture of traditional geologic maps while extending it into the third dimension. Lines on the 2D geologic map (e.g. faults, intrusive contacts, depositional contacts, etc.,) become surfaces, and areas transform into volumes in 3 dimensions. The current 3D geologic map of the Santa Clara Valley is being constructed following a rigorous sequence of procedures. First, point data representing discrete 3D locations on a given geologic surface (e.g. a fault) are assembled from surface geologic mapping, well data, geophysical inversions, seismicity, geologic reasoning, and any other sources available. A numerically defined surface is then passed through these data points in order to predict the position of the geologic surface throughout the 3D map volume. Uncertainty as a function of position is assigned to each surface. Once all important surfaces have been defined in this way, they are assembled into a 3D structure according to rules that specify how the surfaces interact (i.e., which surfaces truncate which). The surfaces, together with the interaction rules, define volumes that correspond to fault blocks and geologic units. Properties are then assigned throughout the 3D geologic map according to xyz location, geologic identity, proximity to surfaces, geologic process model considerations, or some combination of these parameters. Thus the 3D geologic map exists in the computer as a collection of numerically defined surfaces with associated uncertainties, a set of rules that specify spatial interactions where surfaces encounter each other, and a volume distribution of properties with associated uncertainties. Note that because the map is numerical, it is capable of an enormous dynamic range when defining features. Theoretically, strata a few cm thick could be faithfully included in a geologic map that extends through the entire Earth's crust. |
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FAULT
TREE—gives the arrangement of faults that divide the map into
fault blocks. Placement of a fault in the tree structure determines its
relation to other faults. A fault truncates against all faults to its
left.
GEOLOGIC SEQUENCE--gives the arrangement of geologic units within a fault block. Placement of a unit in the vertical stack determines its relative location in the vertical dimension of the map, and the geologic relations (deposition, unconformity,channel erosion) control how the bounding surfaces interact where they intersect each other. |
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Once the 3D map has been assembled within the computer, graphical representations permit the user to examine the map from various directions, slice it to examine its interior, disassemble it to examine individual geologic units, compare it graphically with other geographically defined data, and perform a number of other tasks. While graphical representations are valuable tools with which to make use of the 3D geologic map they are simply graphical extracts from the real 3D geologic map that exists digitally within the computer. Want to know more about our project? |
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