How to use the seismic moment and moment magnitude calculator
Find the seismic moment and moment magnitude of an earthquake from its fault area, slip and rock rigidity. Enter fault area, average slip, shear modulus in the fields above; the seismic moment, moment magnitude mw are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “moment magnitude Mw”, “seismic moment”, “earthquake size from fault”, “calculate seismic moment and moment magnitude”, “find seismic moment”.
Formula
Variables
- A — Fault area (km²)
- D — Average slip (m)
- mu — Shear modulus (Pa)
Worked example
With fault area = 100 km², average slip = 1 m, shear modulus = 30000000000 Pa, the calculator gives seismic moment ≈ 3 × 10¹⁸ N·m; moment magnitude mw ≈ 6.248081.
Frequently asked questions
What is the seismic moment and moment magnitude calculator used for?
Find the seismic moment and moment magnitude of an earthquake from its fault area, slip and rock rigidity. It helps with questions such as “moment magnitude Mw”, “seismic moment”, “earthquake size from fault”.
What is the formula for the seismic moment and moment magnitude calculation?
Seismic moment (N·m) = mu × A × 1e6 × D. Moment magnitude Mw = 2 / 3 × log10([Seismic moment])-6.07. Here A is fault area (km²), D is average slip (m), mu is shear modulus (Pa).
What inputs do I need for the seismic moment and moment magnitude calculator?
You need fault area in km², average slip in m, shear modulus in Pa. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the seismic moment and moment magnitude calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the seismic moment and moment magnitude result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.