Intensity Lab
MMI Scale › Level VIII
VIII

Severe

Severe shaking · Moderate to heavy damage potential

PGA
34 – 65 %g
PGV
60 – 116 cm/s
I II III IV V VI VII VIII IX X

Damage slight in specially designed structures; considerable with partial collapse in ordinary buildings; great in poorly built structures.

Effects

People & Response

  • Drivers strongly disturbed
  • General panic; people difficult to control
  • Difficult to stand even outdoors

Objects & Furnishings

  • Heavy furniture overturned and displaced
  • Sand and mud ejected from ground
  • Springs and wells affected; water levels change

Structures & Environment

  • Brick buildings moderately to extremely damaged
  • Walls fall; stone walls cracked seriously
  • Chimneys, stacks, and columns fall
  • Tree branch and trunk breakage
Typical PGA (ShakeMap) 34 – 65 %g
Typical PGV (ShakeMap) 60 – 116 cm/s
PGA/PGV ranges are approximate; values overlap between adjacent levels. See Instrumental Intensity for details.

Video Example

MMI VIII shaking example video thumbnail
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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.