Special Report 054

Special Report 054

SPE 054

An Investigation of Geological Applications of Archival Lightning Strike Data in the Province of Alberta (North of Latitude 54� North)

Author(s) Robertson, K. Date 2003-11-01

Over the last two decades, the author has heard anecdotes recounted about mines, mineralized outcrops, hills, buildings and other objects that are repeatedly struck by lightning. As well, a search of ancient mining and exploration techniques implied that several high-grade mineral deposits were located by indigenous people observing specific hills or areas being hit more frequently than others by lightning strikes. Examples include the Lightning Ridge deposit discovered by an Aboriginal guide in Australia, the native copper and iron deposits of the Keewenaw Peninsula in Michigan, USA, that were originally found and worked by the Ojibway First Nations, and the Rammelsberg mine at Goslar, Germany, which was discovered prior to 938 AD and was in production from then until 1988.

The purpose of this study is to determine if any reliable geophysical or geological applications can be found for lightning detection networks. In the early 1960s, technology was developed that allowed the monitoring of electrical storm activity from a small number of fixed installations. Lightning detection instruments were initially deployed to protect aerospace launch vehicles and solid-state electronics. By the 1980s, lightning detection (LD) networks were being installed for the use of forestry fire protection branches. As the technology of the monitoring equipment and global positioning advanced the uses for lightning detection, LD networks expanded to provide predictive information for forest fire fighting, as well as insurance claims, storm warnings for sensitive industries and outdoor activities, such as sports events.

This study was launched to investigate whether the archived data from the Province of Alberta lightning detection network could be used to passively map geological features and more specifically assess if lightning strike lineaments might correspond to faults or major fractures in the subsurface bedrock. LD network data for northern Alberta north of about 55�N latitude were provided by Alberta Fire Protection Division. However, because of the large area involved in the study, interpretation of possible lightning strike linears was focused on the Peerless Lake map area (National Topographic System 84B), where a large number of possible linears had previously been identified by the Alberta Geological Survey (AGS). However, the contracted work herein did not provide for an extensive evaluation as to whether many, or even some, of these lightning strike linears are or may be related to underlying fault or fracture zones. This remains to be done under a separate study.

Regarding results, there is, unfortunately, a large location uncertainty associated with the interpreted lightning strike linears. That is, although Global Atmospherics Corporation specification literature indicates the lightning detection network should have a location accuracy of about � 500 m, the scientists with the Alberta Fire Protection Division estimate the lightning detection network actually carries a positioning error of up to about � 6.5 km, dependent on distance from the direction finder. As a result, although the inferred lightning strike linears from this study may be deemed somewhat inconclusive, enough evidence exists to suggest there may be some merit to the concept of using lightning strikes to infer subsurface faults. Having said this, although the lightning strike interpreted results for the Peerless Lake map area are interesting, because as yet no real verification has been done by AGS or others, the inferred linears in this report, and their underlying cause(s), should be treated with caution.

Robertson, K. (2003): An investigation of geological applications of archival lightning strike data in the Province of Alberta (north of latitude 54° north); Alberta Energy and Utilities Board, EUB/AGS Special Report 54, 87 p.