Te Seg We Fae February 21, 1988 News 985-2131 Classified 986-6222 NM. VAN FIRM REVIEWS DAMAGE PREDICTION Distribution 986-1337 56 pages 25¢ A NORTH Vancouver company has been contracted to help estimate the damage that will be wreaked on the. Lower Mainland from a massive earthquake experts predict for the B.C.-Washington-Oregon coast within 200 years. And while most of us don't lose much sleep quaking in our boots thinking about an earthquake that may or may not occur over the next two centuries, focal and regional planners are busying _ themselves making plans for the unthinkable. Keith Robinson, executive man- ager of North Vancouver con- sulting engineer firm Robinson Dames & Moore, has quakes on his mind. His firm has been re- tained by the Greater Vancouver Regional District (GVRD) to review earthquake damage predic- tions for the Lower Mainland. The GVRD regional board ap- proved a $10,000 expenditure last fall for a preliminary study to draft the terms of reference and amass available geotechnical in- formation for a comprehensive earthquake preparedness study. Total cost of the study is estimated at between $100,000 to $200,000. Robinson said the most likely scenario for a local quake predicts an epicentre in the Strait of Georgia or off the west coast of Vancouver {sland with an intensity between 7 and 7.5 on the Richter scale. A darker scenario calls for a major 9 to 9.5 Richter quake in the subduction zone located off the east coast of Vancouver Island. The subduction zone is where sec- tions of the ocean floor are slowly converging with the continent and sliding underneath it. Pressure builds when a section becomes locked. Dr. Dieter Weichert, a seismologist with Canada’s Pacific Geoscience Centre in Sidney, B.C., says the odds of a big subduction earthquake occurring in the next 200 years have increased in the last two or three years from a 50/50 chance to a 70/30 chance. Robinson said from a geotechnical perspective, most of the North Shore is literally on firm ground for a lesser quake. “The most significant structures on the North Shore are situated on CONSULTING engineer firm ex- ecutive manager Keith Robin- son...most of the North Shore is on firm ground. relatively good soil and rock,’’ he said, ‘‘The risk factor is lesser on the slopes. Buildings tend to be founded on glacial, hardpan soil.’’ The most vulnerable areas on the North Shore are the low lands such as lower Norgate and the area around Marine Drive. Looser, sandy soils combined with high water tables can liquify during quakes. : Structural damage variables in- clude earthquake magnitude and - epicentre location; physical make-up of a given building (the more flexible, the better); the soil it is standing on; and shock wave frequency in relation to the natural frequency of a building.