Earthquake duration magnitude
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The concept of Earthquake Duration Magnitude – originally proposed by E. Bisztricsany[1] in 1958 using surface waves only - is based on the realization that on a recorded earthquake seismogram, the total length of the seismic wavetrain – sometimes referred to as the CODA – reflects its size. Thus larger earthquakes give longer seismograms [as well as stronger seismic waves] than small ones. The seismic wave interval measured on the time axis of an earthquake record - starting with the first seismic wave onset until the wavetrain amplitude diminishes to at least 10% of its maximum recorded value - is referred to as "earthquake duration". It is this concept that Bisztricsany first used to develop his Earthquake Duration Magnitude Scale employing surface wave durations.
Earthquake Duration Magnitude (Md ) development
In 1965, Solovev
Md empirical relationships
In two most recent investigations using statistically stable samples for Italian earthquakes (approximately 100,000 events over the period 1981–2002 in the Richter local [ML ] magnitude range of 3.5–5.8)[5] and for Indian earthquakes exemplified by an aftershock sequence of 121 events with Ms (surface wave magnitude) > 4.0 in 2001 in the Bhuj area of northwestern India,[4] the latest empirically derived equations for Md determinations are published:
(Castello et al., 2007)[5]
(Mandal et al., 2004)[4]
Where Md is coda duration magnitude, and T is the coda duration in seconds.
ML from Md
Although conversions between empirically derived "sensitive" seismic parameters such as earthquake magnitude scales is mathematically cautioned as well as physically limited, some
References
- ^ Bisztricsany, E. (1958), "A new method for the determination of the magnitude of earthquakes", Geofiz. Kozlemen, 7 (2): 69–76
- ^ Solov'ev, S.L. (1965), "Seismicity of Sakalin", Bull. Earth Res. Inst., 43, Tokyo Univ.: 95–102
- doi:10.3133/ofr72223
- ^ a b c Mandal, P.; Narasaiah, R.; Raju, P.S.; Chada, R.K. (2004), "Coda duration magnitude scale of 2001 Bhuj aftershocks, India", Current Science, 87 (4), India: 520–527
- ^
- JSTOR 40026547