Earthquakes don't just shake buildings — they stress every system inside and beneath them. For buildings connected to natural gas, the consequences of that stress can be severe, and often unfold in the minutes and hours after the shaking stops.

How Earthquakes Stress Gas Infrastructure

An earthquake generates two types of seismic waves. P-waves (pressure waves) travel fastest and produce predominantly vertical movement — they're the initial jolt. S-waves follow seconds later and cause the lateral movement that does most of the structural damage.

Gas pipework — both the mains beneath the street and the internal pipework inside buildings — is vulnerable to both. The main failure points are:

• Pipe joints and connections, particularly older screwed or lead-caulked joints that lack flexibility
• Where pipes enter buildings, at the demarcation point between the ground-fixed mains and the building's internal system
• Long pipe runs inside buildings, where pipes cross between structural elements that move differently during shaking
• Pressure reduction stations and meters, which contain components that can be damaged by strong ground motion

Inside a Building

In a multi-storey building, the internal gas pipe may run from the street entry in the basement to appliances on upper floors — covering many metres and multiple structural connections. When the building sways, sections of pipework attached to different parts of the structure are pulled in different directions.

A rupture anywhere along that run releases gas into enclosed spaces. Gas-air mixtures are highly flammable across a wide concentration range. Ignition sources — pilot lights, electrical sparks, hot surfaces — are present throughout most buildings. The result can be fire or explosion in a building that may already be structurally compromised and difficult to evacuate.

What the Evidence Shows

Post-earthquake fire is one of the most destructive secondary effects of major earthquakes. In the 1906 San Francisco earthquake, fire caused more damage than the shaking itself. In Christchurch in 2011, gas-related fires added to the destruction in the central city in the hours following the February earthquake.

The time between a pipe rupturing and gas reaching an ignition source can be very short. Manual shutoff — finding the valve, reaching it, turning it — takes minutes. By then the risk has already escalated.

Automatic Isolation

The purpose of an automatic earthquake shutoff system is to close the gas supply at the building entry point the moment seismic activity is detected — before the S-waves arrive, before pipes are stressed to failure, and before gas can accumulate.

An electronic trigger like the MK6 Earthquake Trigger Recorder detects the initial P-wave acceleration and fires a relay within 10 milliseconds, triggering a connected shutoff valve. No human intervention required. No delay. No dependence on someone being present and able to act.

For buildings with long internal gas runs, multiple occupants, or limited evacuation capability — hospitals, apartment blocks, schools — automatic isolation is the only realistic way to interrupt the chain of events before it becomes uncontrollable.

Find out how the MK6 works → or contact us to discuss automatic isolation for your building.