Tambala et al
Greener Journal of Geology and Earth Sciences Vol. 3 (1), pp. 001-012, January 2015.
ISSN: 2354-2268 © 2015 Greener Journals
Manuscript Number: 072114310
The Considerations on Local Magnitude Determination to the Lwiro Seismographical Station
*1Tambala Kongbo Théophile, 2Wafula Mifundu Dieudonné,
3Bagalwa Mateso Luc, 4Jeje Matumaini Albert,
5Maki Mateso Claude
Département de Géophysique, Centre de Recherche en Sciences Naturelles (CRSN), Lwiro, D.R. Congo.
Emails: 2wafulamd @gmail. com, 3lucbagalwa @yahoo. fr, 4jejematch @gmail. com, 5makigeo2013 @gmail. com
*Corresponding Author’s Email: theopunch @gmail. com
About 47 local earthquakes reported by the “Institut pour la Recherche Scientifique en Afrique Centrale (IRSAC) seismographical bulletins and the United states coast Geological survey (USCGS) bulletins in the period from 1965 to 1977 were used to compare seismic energy, 250 local earthquakes reported by the IRSAC bulletins from 1960 to 1964 were used to compare local magnitudes Eml determined by the Lwiro seismogrphical station and the local magnitude scale EM by Richter (1935) and 422 earthquakes recorded at Lwiro station in the period from July to December 2011 were selected to compare the Tsumura (Mtsu), Mukeng (Mmuk) and Lwiro (Mdlwi) duration magnitude. The significant differences marked to p (value) <0,05 between EM and Eml, Dcal and Dbull and Mlricand Mlbull were observed with the T test. The Tsumura (Mtsu), Mukeng (Mmuk) and the Lwiro (Mdlwi) duration Magnitudes had also presented some peculiar features as the Mmuk were lower to those of others and didn't exceed the value of 4. For the epicentral distances superior to 140Km, the Mdlwi gave some lower values to those of Tsumura. The épicentral Distances reported by the IRSAC seismological bulletins were different from those one calculated with epicenters (coordinates) reported by other networks. The EM-Eml difference between the energies determined from the body-wave magnitudes (EM) and those determined from the magnitudes published in the IRSAC seismological bulletins (Eml) was in general lowered to zero. Most of magnitudes reported in the IRSAC seismological bulletins were overestimated, except for the great earthquakes near the stations in the IRSAC network, where magnitudes were not well calculated. This survey showed that some magnitude values published in the Lwiro bulletins should be revalued. A deeper survey could be done, especially on the velocity model to be applied in the region of concern, to allow making the choice between Lwiro magnitudes or those of other networks with a view to survey of seismic hazard assessment. The Lwiro Station should have its own definition of magnitude formulae to take account of the local conditions.
Keywords: earthquake energy, epicentral distance, local magnitude scale, body-wave magnitude, surface-wave magnitude, duration magnitude and maximum amplitude.
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