Lower Mainland, British Columbia
What a major earthquake does to the Lower Mainland
The shaking lasts minutes. Here is what fails, and why the outages can last weeks or months.
What happens after the shaking?
- Hours0–24 h - It is over in minutes, and nothing works- The shaking lasts somewhere between ten seconds and three minutes, depending on how big the earthquake is and where it happens. - An earthquake close to the city is heard before it is felt: a sound like a freight train, then seconds of violent shaking that knock people off their feet, “except for those who remember to drop, cover, and hold on”. More about the shaking. - The power goes out during the shaking, and takes the lights, lifts, tills, fuel pumps and traffic signals with it. Everyone reaches for a phone at once. Cell sites switch to their batteries, but the network is jammed with calls. - Over the next few hours the water pressure falls away as broken mains empty the system. Glass, brick and cladding lie across the pavements and debris blocks streets in every neighbourhood. People are trapped and injured across the region, and the hospitals they are taken to went through the same shaking.
- Days1–7 days - Help reaches main routes before side streets- The taps are dry. Bottled water is the first thing to go from the shops, and the shops do not restock, because food arrives by truck on the same broken roads. Phone service fades as cell-site batteries run down. Sites with generators last as long as their fuel. Cards do not work without power or a network. - Crews clear emergency routes first. Local streets wait, so you may only get as far as you can walk or cycle. The toilet may stop flushing on the first day, because there is no water to spare for it. Family and neighbours are likely to reach you before official help.
- Weeks1–8 weeks - Power and water come back area by area- Power comes back area by area. In downtown Vancouver, BC Hydro says customers could be without power for several weeks, and the system could take years to fully repair. Water follows power. - The sewers stay broken for months, and households use buckets and chemical toilets. Gas returns building by building, as fast as technicians can enter each one and relight every appliance in it. Drinking water comes by truck to distribution points, and people queue for it. Schools and workplaces are closed or have moved.
- Months2 months + - Standing homes can stay closed for months- A building can be standing, look sound, and still be closed for months behind a cordon. Cordons around standing buildings displace more people than collapses. Places to live, contractors and engineers are all hard to find, because the whole region needs them at once. - Utilities run at reduced service long after they are back on. The province’s plan assumes people stay in the region while this goes on. What that means for getting around.
This timeline draws on the two earthquakes the province plans for. It is a scenario, not a forecast.
The weather changes how hard each stretch is. The megathrust scenario is set in a 30 to 40 degree heatwave with wildfire smoke.
Each failure slows the repair of the others. Water needs power for pumps and open roads for crews, and clearing roads needs fuel. Life afterwards takes each system in turn.
None of this is yours to fix. What counts is what you already have at home.
Every system comes back on its own schedule
Start with the one you depend on most. Each card opens a page on what breaks and why.
Communications
Cell-site backup power lasts hours to days, and no rule sets a minimum.
Electricity
Up to two thirds of downtown customers could lose power for several weeks.
Water
Breaks under rivers and inlets take the longest to repair.
Sanitation
Without running water, toilets in apartment towers stop working.
Natural gas
Restoring gas requires a visit to every affected building.
Transportation
A bridge may survive an earthquake without being usable afterwards.
Port, airport and ferry terminals
The airport model expects damage to every bridge onto Sea Island.
Fuel
A service station with full tanks and no power dispenses nothing.
Food
Fresh food depends on regular deliveries.
Dams and reservoirs
The 2024 engineering reviews do not publish an earthquake finding.
Housing
Cordons and failed utilities can keep people out of standing homes.
Health care
Most hospital buildings in the region predate the current seismic code.
Safety and conflict
Most people help one another after a disaster. Theft and violence are the exception.
Where help comes from
A coast-wide earthquake leaves fewer outside agencies able to help.
The region plans for two different earthquakes
The offshore Cascadia megathrust is the one people have heard of. The shallower earthquake underneath the region is the one Natural Resources Canada calls “the greatest earthquake hazard” to west coast cities, because it is closer and more frequent.
They are dangerous to different buildings. Which one matters to you depends on the building you are in and the ground under it. Compare the two scenarios, or read what the shaking does to the ground and the buildings on it.
Cascadia M9 megathrust
A coast-wide disaster, with outside help delayed
- Source
- Offshore subduction interface
- Official simulation
- M9.0 Cascadia Full Rupture, Geological Survey of Canada scenario catalogue
- Shaking in Metro Vancouver
- Moderate intensity, long duration. Three minutes in the province's scenario
- Geographic extent
- Northern California to British Columbia
- Tsunami
- Outer coast; limited effect inside Burrard Inlet
- Mutual aid
- The province states that an overwhelmed United States will be unable to help
- Recurrence
- Sources disagree: 500–600 years on average per NRCan, 400–500 in BC's own documents. Last event 1700
Shallow crustal M7
More violent shaking in Metro Vancouver
- Source
- Strait of Georgia shallow crust, 3–4 km deep
- Official simulation
- M7.0 Georgia Strait, same catalogue, and the province's own primary planning scenario
- Shaking in Metro Vancouver
- High intensity, short duration. 10 to 20 seconds of violent shaking in the province's scenario
- Geographic extent
- Concentrated and local
- Tsunami
- Not the primary concern
- Mutual aid
- BC's plan assumes agencies outside the local impact area remain available
- Recurrence
- Roughly once every 1,500 years in the region, according to the province's scenario
Everything here comes from published documents
Every fact here comes from a published document, most of them written by governments, utilities and the engineers they hire. Where nobody has published an answer, the page says so. Where two official documents disagree, you see both.
Durations are given as the source gives them, never more precise. How this site works explains the method, the sources page lists every document, and contribute explains how to report an error.
Start with food and water
- British Columbia asks every household to keep at least two weeks of emergency supplies.
- You do not need to assemble everything at once. Check what you already have, then add water and food that keeps. The preparation guide shows how much to keep and what to add next.
Sources on this page
Numbered in the order they are cited. Each entry links back to where it is used.
- [1]ReportProvincial Earthquake Immediate Response StrategyMinistry of Emergency Management and Climate Readiness, Province of BC · 2022Rev. 1.1, 135 pp: the crustal M7.0 Greater Vancouver planning scenario, its impacts, the planning assumptions, the formal mutual-aid instruments, and the two-weeks-versus-72-hours pair on p. 42Open the document ↗
- [2]ReportDisaster and Climate Risk and Resilience Assessment: Provincial ReportEMCR and Ministry of Energy and Climate Solutions, Province of BC · 2025Incl. ch. 5 §5.6 Extreme Events (the M9.0 Cascadia scenario)Open the document ↗
- [3]ReportThe M9 Cascadia Megathrust Earthquake of January 26, 1700NRCan / Earthquakes CanadaThe magnitude appears in the title only, and the page credits Japanese records and subsidence, not tree ringsOpen the document ↗
- [4]ReportEarthquake and Tsunami Preparedness GuidePreparedBC / EMCR, Province of BC · 2024"at least two weeks", three times; four litres per person per day; zero occurrences of "72 hours", "72-hour", "three days" or "three-day"Open the document ↗
- [5]ReportEmergency preparedness poll: 39 per cent of Metro Vancouver respondents had purchased or prepared an emergency kit, 38 per cent province-wide and down eight points from the same firm's May 2019 survey; 28 per cent had a plan for contacting family, 22 per cent an agreed meeting place. 800 British Columbians online, 31 July to 3 August 2021, weighted to census figures for age, gender and region, margin of error ±3.5 percentage points 19 times out of 20. The most defensible regional figure in the public record, and a kit is not a fortnight of suppliesResearch Co. · 2021Open the document ↗