Mercalli vs JMA Crosswalk Lookup
Crosswalk between JMA instrumental scale and equivalent MMI range.
Description
Crosswalk between JMA instrumental scale and equivalent MMI range.
Mercalli vs JMA Crosswalk Lookup is a focused tool for the following task. Crosswalk between JMA instrumental scale and equivalent MMI range. It reports MMI low, MMI high, Descriptor from the values you provide rather than inventing measurements, coefficients, or professional judgment that are not part of the input.
When to use Mercalli vs JMA Crosswalk Lookup
Use this seismology calculation to reproduce a stated convention, screen observations, or compare scenarios whose units, coordinate conventions, catalog selection, and model assumptions are known.
- I_JMA
- Required number. JMA intensity.
The cited overview of Seismic intensity scales supplies background for the terminology and domain context used by this tool.1
How Mercalli vs JMA Crosswalk Lookup works
Crosswalk between JMA instrumental scale and equivalent MMI range. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.
- MMI low
- Returned number. Lower bound MMI equivalent.
- MMI high
- Returned number. Upper bound MMI equivalent.
- Descriptor
- Returned string. Shaking descriptor.
Limitations and assumptions
- Earth structure, source geometry, path effects, site response, instrument response, catalog completeness, uncertainty, and the fitted range can dominate the accuracy of simplified seismic calculations.
- I_JMA must be at least 0.
- I_JMA must be no greater than 7.
- Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.
Alternative or Complementary approaches
For analysis or hazard decisions, retain uncertainty and provenance and compare the result with waveform processing, calibrated regional models, and guidance from qualified seismologists or the responsible agency.
References
-
Seismic intensity scales — Wikipedia contributors
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- JMA Intensity From PGV Converter
Japan Meteorological Agency instrumental intensity from PGV (cm/s): I_JMA = 2.68·log₁₀(PGV) + 2.29 (approx).