Figure 1 (Stein and Wysession, 2003)

Figure 2 (Stein and Wysession, 2003) ____________________________________________Figure 3 (Stein and Wysession, 2003)
Figure 4 (Sten and Wysession 2003)
Figure 5 (Stein and Wysession, 2003)

Seismic Profiles: Imaging the Overlap

Introduction
Seismic reflection profiles have been the key tool in oil and gas exploration. With seismic reflection profiles, geologists can identify areas which most likely contain a reservoir large enough to make drilling feasible . In the last 50 years, much effort has been made to image the Rocky Mountain region of the United States with seismic profiles in order to find oil and gas reserves (Figure 1). As a result, subsurface deformation features such as thrust faults from the Sevier Orogeny and reverse faulting from the Laramide Orogeny have been imaged and then used to interpret the tectonic story of the western U.S.

The Method
The seismic reflection method uses active sources, or artificial earthquakes, to measure the travel times of the Primary seismic waves from the source to a transect of sensors. The primary goal to identify and image reflectors in the subsurface. Reflectors depend on the density and speed contrasts between two layers which controls the angle at which the P-wave reflects. (Figure 2).

By choosing a common reflector point at a common depth for each sensor (Figure 3), a common reflector for each sensor will represent the same surface assuming it is horizontal. By taking into account the offiset distances of each sensor and any diffraction of the propagating wave due to non-horizontal surfaces this hyperbolic reflector curve will flatten. All the traces are summed for the sensor above the common depths (Figure 4).

These outpust traces are created for each sensor, then they are combined to make one image (Figure 5).
Example of seismic reflection in the Laramide/Sevier Overlapping Region.