What is moment magnitude a function of?
What is moment magnitude a function of?
Moment Magnitude (MW) is based on physical properties of the earthquake derived from an analysis of all the waveforms recorded from the shaking. First the seismic moment is computed, and then it is converted to a magnitude designed to be roughly equal to the Richter Scale in the magnitude range where they overlap.
What is μ in the following expression of seismic moment?
Seismic moment can be defined as (6)M0=μAfD¯=2μES/Δσwhere μ is the shear modulus of the crust, Af is the rupture area of the fault, D¯ is the coseismic displacement averaged over the rupture area, Δσ is the static stress drop averaged over the rupture area, and ES is the radiated seismic energy.
What is seismic moment tensor?
A mathematical representation of the movement on a fault during an earthquake, comprising of nine generalized couples, or nine sets of two vectors. It is often represented with “beach balls” just like the focal mechanism (or fault plane solution). See also seismic moment and fault plane solution.
How is moment magnitude calculated?
In particular, for very large earthquakes, moment magnitude gives the most reliable estimate of earthquake size. Moment is a physical quantity proportional to the slip on the fault multiplied by the area of the fault surface that slips; it is related to the total energy released in the earthquake.
How is the moment rate of an earthquake defined?
The seismic moment rate is defined as the product of the rigidity μ, the area S, and the average slip rate vslip. The variation in slip rate during slow earthquakes is poorly understood. The simplest assumption is a constant vslip, which leads to a seismic moment rate .
How is the seismic moment related to the slip rate?
Based on the seismic moment and the well-known GR law, several authors (e.g., Campbell 1977, Molnar 1979, Anderson 1979, and Papastamatiou 1980) developed various relationships between the earthquake occurrence parameters and the crustal deformation rates ( slip rate ).
How is the seismic moment related to a torque?
The connection between seismic moment and a torque is natural in the body-force equivalent representation of seismic sources as a double-couple (a pair of force couples with opposite torques): the seismic moment is the torque of each of the two couples. Despite having the same dimensions as energy, seismic moment is not a measure of energy.
How is the seismic moment represented in a Cartesian system?
While the injection of a volcanic fluid or a thermal expansion of a fluid-filled crack occurs, a sudden volume increase Δ V is observed and the fracture acts as a radiating seismic source. The seismic moment tensors of these sources can be represented in a Cartesian system of coordinates ( Figure 11.6 ). Figure 11.6.