Intensity Lab
MMI Scale › Level III
III

Weak

Weak shaking · None damage potential

PGA
0.3 – 1.4 %g
PGV
1.1 – 3.4 cm/s
I II III IV V VI VII VIII IX X

Felt quite noticeably by persons indoors. Many people do not recognize it as an earthquake. Vibrations similar to the passing of a truck.

Effects

People & Response

  • Felt noticeably indoors, especially on upper floors
  • Many do not recognize it as an earthquake
  • Duration of shaking can be estimated

Objects & Furnishings

  • Chandeliers and hanging objects shake
  • Vibration similar to passing heavy truck
  • Dishes and windows may rattle slightly

Structures & Environment

  • Standing cars rock slightly
  • No structural damage
Typical PGA (ShakeMap) 0.3 – 1.4 %g
Typical PGV (ShakeMap) 1.1 – 3.4 cm/s
PGA/PGV ranges are approximate; values overlap between adjacent levels. See Instrumental Intensity for details.

Video Example

MMI III shaking example video thumbnail
Watch on YouTube ↗
← II Weak Light IV →

Descriptions are verbatim from the USGS MMI Scale, based on Wood & Neumann (1931) and Richter (1958). Source: USGS Modified Mercalli Intensity Scale .

Instrumental intensity values and PGA/PGV ranges from USGS ShakeMap V4 Technical Documentation (Worden et al.). Intensity Lab reports MMI derived via the Worden et al. (2012) GMICE, interpolated from USGS ShakeMap. PGA/PGV ranges are approximate; actual values overlap between adjacent levels.