UC San Diego

Controlled source electromagnetic methods have been used in exploration of the offshore environment for over 50 years to map the resistivity structure of the earth. Developments in both instrumentation and computational power have lead to many advancements that have led to discoveries and insights about the subsurface. One of these advancements has been the development of towed EM acquisition systems. One system the Marine EM Lab at Scripps Institution of Oceanography has developed is a shallow water system, named Porpoise, can be used in water depths as shallow as 5m. In May of 2014, a one day field test of this new shallow water acquisition system took place offshore of Del Mar and Torrey Pines State Natural Reserve, California. The data from this field test corresponds with previous interpretations of paleochannels directly offshore modern day San Dieguito and Soledad Valley river outflows. With resistivity data, it is possible to indirectly map porosity in the near surface and to map geological features. The data dense and economical operation of the Porpoise acquisition system can be used to map resistivity and indirectly porosity in a variety of shallow water marine environments. This field test proves the viability and limitations of the Porpoise system