Seismicity Study of Botswana from 1966 to 2012 - International Journal of Geosciences

IJG > Vol.9 No.12, December 2018

International Journal of Geosciences

Volume 9, Issue 12 (December 2018)

ISSN Print: 2156-8359 ISSN Online: 2156-8367

Google-based Impact Factor: 0.56 Citations h5-index & Ranking

Seismicity Study of Botswana from 1966 to 2012 ()

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DOI: 10.4236/ijg.2018.912043 986 Downloads 2,387 Views Citations

Author(s)

Bokani Nthaba^1*, Rapelang E. Simon², Ghebrebrhan M. Ogubazghi³

Affiliation(s)

¹Botswana International University of Science and Technology (BIUST), Palapye, Botswana.
²Physics Department, University of Botswana, Gaborone, Botswana.
³Department of Earth Sciences, Eritrea Institute of Technology, Asmara, Eritrea.

ABSTRACT

The history of Botswana’s major seismic events has been initiated by two earthquakes that occurred on the 11^th of September and 11^th of October 1952 with ML Richter magnitudes of 6.1 and 6.7, respectively, in the Okavango Delta Region (ODR). Not much is known and well documented about the seismicity of a larger coverage of Botswana primarily because over the years, local seismic stations were biased to the north-western part of Botswana, to monitor the more seismogenic ODR. The objective of this study is to use data from the International Seismological Centre (ISC) bulletin for the period 1966-2012 to estimate the relative size distribution of seismic events (b-value), the rate of seismic activity (a-value), and associated stress condition prevailing in Botswana to assist in the quest of hazard mitigation. This study shows that micro-seismic activities of magnitude ranging from 1.3 to 5.7 are distributed not only on the northern part of Botswana, but also in other parts of the country such as the Southern (including Kweneng East and West), Central and Eastern Botswana. Based on 327 events extracted from data compiled by the ISC, the frequency-magnitude distribution (FMD) of earthquakes in Botswana from 1966 to 2012 was estimated with b-value and a-value for the entire catalogue found to be 1.2 and 6.3, respectively, implying a region of low stress dominated by small to moderate events. The minimum completeness magnitude (M_C), a value that indicates the lowest magnitude above which all seismic events are reliably recorded was found to be 3.8. From this analysis, annual probabilities of occurrence for M4 and M5 events were found to be 67.2% and 4.3%, respectively, while M6 or larger event has an annual probability of 0.3%.

KEYWORDS

b-Value, Catalogue, Completeness Magnitude, Okavango Delta Region, Seismicity

Share and Cite:

Nthaba, B. , Simon, R. and Ogubazghi, G. (2018) Seismicity Study of Botswana from 1966 to 2012. International Journal of Geosciences, 9, 707-718. doi: 10.4236/ijg.2018.912043.

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