The search for "Yvonne": a case example of the delineation of a grave using near-surface geophysical methods.

Shallow electromagnetic (EM) and ground-penetrating radar (GPR) surveys were conducted in an area north of Auckland, New Zealand to assist the search for human remains. The body had been buried for almost 12 years in a plantation forest that was irregularly disrupted and modified by tree harvesting and the partial removal of stumps. EM identified anomalous areas of potential interest, because a target need only be nearby to generate an EM response. GPR was then used to map subsurface layering, layering disruption, and buried objects, immediately adjacent to an EM anomaly. Because of the nature of the site, numerous geophysical anomalies were present. GPR was particularly sensitive to site disturbance resulting from the forestry operations. An isolated EM anomaly on the fringes of an expanded survey area was coincident with the location of the body. Whether for criminal investigations or for archaeological work, a combination of geophysical techniques is recommended.