Vol 6, No 3 (2015) > Civil Engineering >

Development of an Extended Hara Model for Mw Determination of Moderate-Magnitude Earthquakes

I Nyoman Sukanta, Widjojo A. Prakoso, Tommy Ilyas, Masyhur Irsyam

 

Abstract:

This study discusses the evaluation of Hara’s model to
estimate seismic moment magnitude (MW) by using teleseismic waveform
data, and then presents the development of an extended Hara model. Both models
use the maximum amplitude of displacement and epicenter distance, as well as
the duration of high-frequency energy radiation, of the vertical component of
earthquake P-wave records. Nineteen moderate-magnitude (5.0 £ MW£ 7.0), shallow (depths £ 70 km), Sumatra subduction megathrust earthquake data
sets recorded by the KAPI seismograph station (Kappang, South Sulawesi) in 2010
and 2011 were used in this study. The analysis is performed to obtain the
maximum amplitude of displacement, epicenter distance, and the duration of
high-frequency energy radiation on the first arriving P-wave. The main results
show that Hara’s model (2007) overestimates MW to be less than 7.0
compared with that obtained from the Global Centroid Moment Tensor (CMT)
catalog. The extended Hara model was developed with the use of the same basic
equation, and the resulting coefficients are α = 0.538792, β = 0.783840, γ =
0.242616, and δ = 4.929095. The mean and standard deviation of the difference
between the extended Hara model and the Global CMT catalog are 0.01 and 0.14,
respectively.

Keywords: Earthquake; Hara’s model; Moment magnitude (Mw); Sumatra subduction megathrust

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