Uncertainty Estimation of P Wave Velocity and Layer Boundaries Using Seismic Refraction with Synthetic Horizontal Layered Geological Model

This paper conducts a series of studies on the uncertainty problems encountered in the role of personnel in the implementation processing of seismic refraction. In order to increase the reliability result of the seismic refraction method, evaluating the seismic refraction method is fundamental. The main paper's purpose is to evaluate seismic refraction and reduce uncertainty in seismic refraction considering human interpretation results. We analyze the uncertainty of seismic refraction separately in two-part: first arrival picking processing and grouping of data into a unified layer with identical wave velocity based on the time-distance curve (T-D curve). This study utilized forward modeling results of a synthetic geological model in which the boundaries of layers (gently dip straight line) and the P wave velocity (Vp) of each layer was given. The model is made up of five layers, with velocity increasing with depth (Vp = 700 m/s, 1100 m/s, 1500 m/s, 1800 m/s, and 2200 m/s from top to bottom). The uncertainty will consider based on the P wave velocity value and thickness layer. According to the first arrival picking results of seven operators, we discovered high uncertainty (11.2 %) in the first layer. On the grouping layer processing, high uncertainty of P wave velocity (11.8 %) and thickness layer (16.3%) in the first layer. Adding information on thickness data in processing seismic refraction effectively reduces uncertainty to 7.1 %, and P wave velocity data can reduce uncertainty to 1.7 %. Thickness data and velocity data effectively reduce uncertainty in grouping layer processing. However, uncertainty from first arrival picking still exists.

Keywords: Seismic refraction, time-distance curve, Synthetic case, Forward modeling.