By: Bill White, BC Housing
The recent earthquake (magnitude 7.7) on 27 October 2012 at 20:04 hours in the evening with epicentre off the west coast of Haida Gwaii was yet another wake-up call for those of us living in British Columbia. Fortunately this was a “no fatality, no damage” event. This could not have been a better timed event to practice our earthquake response. In the emergency preparedness community we would never have been allowed to conduct an exercise on a Saturday night!
So how did we do?
From notification through to response there were some issues. Earlier that month many BC citizens had participated in the “Drop – Cover – Hold on” drill as part of BC Shakeout Drill on 18 October. However an elected official in Queen Charlotte City, as reported to one media organisation, stood in a doorway; while others in the same community rushed outside and reported listening to electrical wires slapping from side to side, thereby putting themselves in more danger than if they had stayed inside their homes. The media, unfortunately will inevitably interview someone who has done the wrong thing, thereby contributing to the ongoing reinforcement of unsafe and inappropriate practices.
Others although they experienced the warning from strong ground shaking were waiting to be told to evacuate to higher ground to avoid the potential inundation from a tsunami. So, more teaching and training of citizens to reinforce the appropriate procedures is required.
A “road map” for Integrated Provincial Damage Assessment and Inspection of buildings has been developed. This was tested during the flooding that occurred in the Shuswap in June 2012. This would have been the protocol to follow if there had been the requirement to conduct damage assessment in the communities of Haida Gwaii.
BC Housing used the earthquake event as an opportunity to conduct a Rapid Damage Assessment exercise. Properties in Prince Rupert, Terrace, Kitimat, Masset and Queen Charlotte City were assessed in the days following the earthquake.
The Building Code
Our most successful natural hazard mitigation strategy has been the development of the National Building Code. This is adopted, adapted and enforced by the authority having jurisdiction which in British Columbia (BC) is the Province, resulting in the BC Building Code.
In the BC Building Code, as in the national code, buildings are categorised by importance as a function of use and occupancy. There are four categories which are low, normal, high and post-disaster. Low is for low occupancy and storage buildings. Normal covers buildings such as residences, offices, hotels etc. High is for buildings that are likely to be used as post-disaster shelters including schools and community centres. This category also includes manufacturing and storage facilities containing toxic, explosive or hazardous materials in quantities considered to be dangerous to the public if released. Post-disaster buildings are those that are essential for the provision of services in the event of a disaster. Some examples include hospitals, power stations, air and marine traffic control centres, water treatment facilities, emergency operation centres, police and fire stations, and communication centres.
For earthquake loads the Importance Factor related to the Importance Categories are as follows; 0.8 for low category, 1.0 for normal category, 1.3 for high category and 1.5 for post-disaster category.
In comparison to normal category building a high category building is designed to sustain a 30% higher earthquake load and for post-disaster it is 50% higher than normal. For normal category buildings the intent is to design for life safety so the design earthquake will not cause the building to collapse and occupants will be able exit the building. However the building is not designed for continued functionality and will likely require repair to get it back into operation. It is only when designing for high and post-disaster that continued functionality of the building is considered.
These are all the components that are attached to a building or all the furnishings and equipment that are inside a building. If these are not restrained properly these components move around during an earthquake. These are more likely to be the cause of injuries and loss of operation of the building than damage to the structure. The risk of these components can be addressed by complying with CSA-S832 – Seismic Risk Reduction of Operational and Functional Components (OFCs) of Buildings.
What about critical infrastructure? For an individual or family this is likely to be their home or work place depending on the business continuity plan for that organisation. At a community level critical infrastructure is generally related to facilities and services for life saving and life sustainment.
Criticality of Critical Infrastructure
Within our built environment, how do we identify what infrastructure is critical and how critical? Infrastructure can be evaluated by using the British Columbia Critical Infrastructure Rating Workbook as posted on the Emergency Management British Columbia website. The rating criteria are based on those used in the national Vital Points Programme and then reworked by the emergency preparedness community in BC. Events such as planning for the spring freshet in 2007 and for the 2010 Winter Olympics led to significant improvements including improved analysis of interdependencies.
The rating of consequence of loss of infrastructure, based on a loss/failure scenario with the maximum credible damage, provides the owner/operator with the criticality rating which also identifies the priority for mitigation or restoration.
Critical Infrastructure Monitoring
What about monitoring of critical infrastructure for seismic motion? The British Columbia Smart Infrastructure Monitoring System (BCSIMS) is an initiative by the BC Ministry of Transportation and Infrastructure, Natural Resources Canada and the University of British Columbia. This is a network of strong motion detectors connected to the internet. The detectors, about the size of car battery, are relatively cheap, relatively easy to install, use less than 6 watts of power per year and draw less 100 bytes/second intermittently via an internet connection.
These detectors can provide useful information prior to an earthquake. Data from the detectors can be used for seismic micro-zonation, for the development of realistic scenarios for response exercises and the planning for the response to a damaging earthquake. The detectors can also potentially be used for early warning by means of detecting P waves. During an earthquake the detectors will provide real-time information on severity of motion, which will assists in prioritizing and identifying where life saving and damage assessment resources need to be deployed.
Wood Frame Buildings
Referring back to the review of the BC Housing residential buildings on Haida Gwaii, what was impressive is how resilient the wood frame buildings were. With the improved strengthening provisions of Part 9 (housing and small buildings) of the BC Building Code, this bodes well for a reduction in potential injuries and improved resilience of infrastructure.
Now if only we could progress from a building code based on life safety to one based on operational capability thereby improving infrastructure sustainability and resiliency!