Fluctuations in oil flow before and after earthquakes

Abstract

INTEREST has been growing recently in geophysical phenomena which occur near the time of earthquake events. We have been observing the flow of oil from wells in the Gulf of Suez and have noticed that remarkable fluctuations in flow occurred near the time of certain nearby earthquake events. The Gulf of Suez is considered to be an opening tensile region with Sinai moving away from the African continent1. The earthquakes occurred close to the bifurcation point of the Gulf of Suez and Eilat and the wells are about 100 km north from this point in the Gulf of Suez (Fig. 1, insert). The oil was driven up by natural pore pressure and was not pumped. Measurements of oil flow were made once a month. Figure 1 shows that from about January 1968 to June 1969, and from about April 1971 to July 1972, large fluctuations occurred in oil outflow. Also, within these periods arid in particular towards the end, several moderate earthquakes occurred. In the first period there was an event on March 31, 1969 (magnitude 6.1) plus a few foreshocks and many aftershocks reaching a maximum magnitude of 5.0. In the second period there were events on July 8, 1971 (magnitude 4.8), January 12, 1972 (5.1) and June 28, 1972 (5.6). Except for these periods the oil outflow was on the whole more stable and the earthquakes that did occur were of smaller magnitude, the largest ones being of magnitude 4.8 on December 30, 1969 and April 28, 1970. (No earthquakes occurred from January 1964 to February 1969.) The choke openings at the tops of the pipes were varied from time to time but after examination it seems to us that these variations did not cause the observed fluctuations.