Richter magnitude scale

The Richter magnitude scale (ML, also Richter scale) assigns a magnitude nummer tae quantify the size o an yirdquauk. The Richter scale, developed in the 1930s, is a base-10 logarithmic scale, that defines magnitude as the logarithm o the ratio o the amplitude o the seismic waves tae an arbitrar, minor amplitude, as recordit on a staundardised seismograph at a staundart distance.


Magnitude Description Mercalli intensity Average yirdquauk effects Average frequency o occurrence (estimatit)
1.0–1.9 Micro I Microyirdquauks, nae felt, or felt rarely. Recordit bi seismographs.[1] Conteenual/several million per year
2.0–2.9 Minor I tae II Felt slichtly bi some fowk. No damage tae biggins. Ower ane million per year
3.0–3.9 III tae IV Eften felt bi fowk, but verra rarely causes damage. Shakin o induir objects can be noticeable. Ower 100,000 per year
4.0–4.9 Licht IV tae VI Noticeable shakin o induir objects an rattlin noises. Felt bi maist fowk in the affectit aurie. Slichtly felt ootside. Generally causes none tae minimal damage. Moderate tae signeeficant damage verra unlikely. Some objects mey fall off shelfs or be knockit ower. 10,000 tae 15,000 per year
5.0–5.9 Moderate VI tae VII Can cause damage o varyin severity tae puirly constructit biggins. At maist, none tae slicht damage tae aw ither biggins. Felt bi iveryane. 1,000 tae 1,500 per year
6.0–6.9 Strang VIII tae X Damage tae a moderate nummer o well-biggit structurs in populatit auries. Yirdquauk-resistant structurs survive wi slicht tae moderate damage. Puirly designed structurs receive moderate tae severe damage. Felt in wider auries; up tae hundreds o miles/kilometres frae the epicentre. Strang tae veeolent shakin in epicentral aurie. 100 to 150 per year
7.0–7.9 Major X or greater[2] Causes damage tae maist biggins, some tae pairtially or completely collapse or receive severe damage. Well-designed structurs are likely tae receive damage. Felt athort great distances wi major damage maistly leemitit tae 250 km frae epicentre. 10 to 20 per year
8.0–8.9 Great Major damage tae biggins, structurs likely tae be destroyed. Will cause moderate tae hivy damage tae kibble or yirdquauk-resistant biggins. Damagin in lairge auries. Felt in extremely lairge regions. Ane per year
9.0 and greater At or near tot destruction – severe damage or collapse tae aw biggins. Hivy damage an shakin extends tae distant locations. Permanent cheenges in grund topografie. Ane per 10 tae 50 years


  1. This is what Richter wrote in his Elementary Seismology (1958), an opinion copiously reproduced afterwards in Earth's science primers. Recent evidence shows that earthquakes with negative magnitudes (down to −0.7) can also be felt in exceptional cases, especially when the focus is very shallow (a few hundred metres). See: Thouvenot, F.; Bouchon, M. (2008). "What is the lowest magnitude threshold at which an earthquake can be felt or heard, or objects thrown into the air?," in Fréchet, J., Meghraoui, M. & Stucchi, M. (eds), Modern Approaches in Solid Earth Sciences (vol. 2), Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes, Springer, Dordrecht, 313–326.
  2. "Anchorage, Alaska (AK) profile: population, maps, real estate, averages, homes, statistics, relocation, travel, jobs, hospitals, schools, crime, moving, houses, news". Retrieved 2012-10-12.