Abstract: A method of analyzing seismic survey data in which a transfer function for a geological model is derived by ray tracing techniques applied to theoretical data and the transfer function is applied to actual survey data in order to calculate reflection points (50) and/or other attributes for each shot (42)/receiver (44) pair. The number of ray tracing calculations which have to be performed in deriving the model transfer function can thus be controlled. A sufficiently accurate transfer function can be derived using theoretical data representing substantially fewer shot (42)/receiver (44) pairs than are used in the traditional ray tracing solution applied directly to actual survey data. Attribute values for actual source (42)/receiver (44) pairs are estimated by interpolating the transfer function data.

Abstract: A method of analysing seismic survey data in which a transfer function for a geological model is derived by ray tracing techniques applied to theoretical data and the transfer function is applied to actual survey data in order to calculate reflection points (50) and/or other attributes for each shot (42)/receiver (44) pair. The number of ray tracing calculations which have to be performed in deriving the model transfer function can thus be controlled. A sufficiently accurate transfer function can be derived using theoretical data representing substantially fewer shot (42)/receiver (44) pairs than are used in the traditional ray tracing solution applied directly to actual survey data. Attribute values for actual source (42)/receiver (44) pairs are estimated by interpolating the transfer function data.

Abstract: A roofing membrane heat seal indicator provides a positive, visually perceptible indication that a joint or seam has been raised to a sufficiently high temperature to achieve a proper seal. The heat seal indicator is applied adjacent and parallel to an edge of a roofing membrane which will be arranged on a roof to form the upper (exposed) surface of an overlapping membrane seam. As the adjacent surfaces of the overlapped membranes are heated, heat passes through the membrane to the heat seal indicator. The heat seal indicator may be a temperature sensitive ink pigmented with material that changes color upon being subjected to a temperature indicating that the membrane surface has been subjected to a sufficiently high temperature to achieve an appropriate seal. Alternatively, the indicator may be an adhered layer of a ground or flaked polymer, such as polyethylene, which is initially opaque but melts to become translucent, thereby indicating obtainment of a proper sealing temperature.