Intensity Lab
MMI Scale › Level IV
IV

Light

Light shaking · None damage potential

PGA
1.4 – 3.9 %g
PGV
3.4 – 8.1 cm/s
I II III IV V VI VII VIII IX X

Felt by many indoors, few outdoors. At night some awakened. Sensation like a heavy truck striking the building.

Effects

People & Response

  • Felt by many indoors, few outdoors during the day
  • Some people awakened at night
  • No general alarm; mostly surprise

Objects & Furnishings

  • Dishes and windows rattle alarmingly
  • Hanging objects swing noticeably
  • Liquids slightly disturbed in open containers
  • Small bells ring

Structures & Environment

  • Walls creak noticeably
  • Cars rock noticeably
  • No structural damage
Typical PGA (ShakeMap) 1.4 – 3.9 %g
Typical PGV (ShakeMap) 3.4 – 8.1 cm/s
PGA/PGV ranges are approximate; values overlap between adjacent levels. See Instrumental Intensity for details.

Video Example

MMI IV shaking example video thumbnail
Watch on YouTube ↗
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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.