oa Fractal Dimension of a Trace as a Tool for First Arrival Picking

Our eyes can recognize the arrival time of the signals by comparing the recorded amplitudes in various seismic traces. In this article we are trying to imitate this natural ability to find out a mathematical tool instead of eyes. Fractals are mathematical models, which are able to the job by analyzing the changes in the recorded amplitudes. We present the results of applying an algorithm to pick automatically first arrival times in seismic records. The algorithm detects the presence of a signal by analyzing the variation in fractal dimension along the trace. Among the different evaluated methods, “divider method” was found to be the most suitable method for calculating the fractal dimension. A change in dimension was found to occur close to the transition from noise part of a trace to its signal plus noise part, which is in fact the first arrival. We found that the nature of this change varies from trace to trace, but a detectable amount of change is always occurring.