Tukuk-OSHow to Read Earthquake Data
From seismograph numbers to a safe decision in 60 seconds
Every row in our earthquake complex comes from the United States Geological Survey (USGS), the public science agency that records more than 20,000 earthquakes a year with a global seismograph network. This is what you need to read them.
Magnitude: a logarithmic scale
Every step of 1 magnitude means 10× the amplitude and ~32× the energy. An M6.0 releases roughly 32 times the energy of an M5.0 — which is why the gap between "6.1" and "5.4" in the news is not a small thing.
| Magnitude | Class | Typical effect |
|---|---|---|
| < 2.5 | micro | only seismographs pick it up |
| 2.5 – 5.0 | light | often felt near the epicentre; minor damage |
| 5.0 – 6.0 | moderate | serious damage where people live; Sabah 2015 = 6.0 |
| 6.0 – 7.0 | strong | widespread destruction within a radius of about 100 km |
| 7.0 – 8.0 | major | destruction over a wide area; the 2018 Sulawesi Sea quake = 7.5 + liquefaction + tsunami |
| > 8.0 | great | ruptures whole volcanic chains; Aceh 2004 = 9.1, a tsunami that crossed an ocean |
Depth: the factor that decides what you feel
A quake at 10 km is felt far harder at the surface than one of the same magnitude at 200 km. The Sabah zone is usually shallow (<20 km), which is why even small tremors are felt in Kota Kinabalu. Deep events (>300 km) under the Philippine Sea rarely do damage even when their magnitude is large.
Why Sabah shakes while KL usually does not
Borneo sits on the fairly stable Sunda Plate, but its eastern edge is squeezed by the Sulu and Philippine Sea plates — that is what formed the active Lingkabau, Pitas and Tambon faults. The Peninsula is on the back row: most tremors reported in Klang or Penang are distant Sumatran waves, amplified by soft ground and tall buildings.
Tsunami: when a warning deserves to be taken seriously
The tsunami-warning signature = an M7+ quake on a sea fault at a depth below 30 km. In Malaysia, the west coast of Sabah and eastern Sarawak are most exposed to the Sulawesi Sea. If shaking by the water lasts more than 20 seconds, move to higher ground straight away — do not wait for the official siren.
The gold protocol: Drop, Cover, Hold
- Drop — get down on your hands and knees before the shaking throws you over.
- Cover — crawl under a table and shield your head & neck. No table? An interior corner, away from mirrors.
- Hold — hold on where you are until the shaking stops; moving around while the ground still moves is the most common cause of injury.