Murray Roed contributed to a book that includes Oliver (Okanagan Geology South, Geologic Highlights of the South Okanagan). The book is mainly an overview with detail about certain localities, features and some geologic history of glacial events.
The Chronicle contacted Roed, who consulted with a geological expert about fault lines in the area.
Oliver has several fault lines. The main one, which has not been active for 50 million years, is the Okanagan Valley Fault Zone. It extends from south of the border to north of Okanagan Lake. It slopes gently to the west and lies mainly hidden beneath the deep glacial lake and river deposits that fill the valley.
Most of the rocks west of the valley slid westward on this fault, possibly as much as 50 kilometres. A smaller fault, running north-south, lies just west of Tucelnuit Lake. It has not been studied in detail and its slope and sense of motion are not known.
Roed said any fault, no matter how old, is a zone of weakness in the earth’s crust that can “jump” again if affected by earthquake energy. It is not possible to predict which ones might become active and hazardous and which ones may not.
Roed said it is impossible to predict when and where there might be an earthquake and secondly, the strength and location of any earthquake will determine whether its energy will activate a given fault or not.
He noted much of the damage to buildings occurs not from the actual vibration (although it could cause some) but the downslope shifting of soil and rubble that the structure is built on. Although hard to avoid in a dirt-filled valley, building on dirt on a slope is more dangerous than on solid rock.
Roed noted that detailed local mapping and seismic measurements of buried features would be prudent, but would still not help predict the timing or effects of another earthquake.
