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ssahara2016 [2017/06/13 14:29]
Valerio Poggi [Seismicity Parameters]
ssahara2016 [2017/06/13 14:47]
Valerio Poggi [The SSA-GEM Earthquake Catalogue]
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 An up-to-date earthquake catalogue for Sub-Saharan Africa with homogenous magnitude representation (MW) was obtained by augmenting available global catalogues (e.g. //​ISC-Reviewed//,​ //​ISC-GEM//,​ //GCMT//, //GEM Historical Catalogue//​) with information from local agencies and regional projects, particularly from AfricaArray temporary deployments (//The Tanzanian Broadband Seismic Experiment//;​ //The Ethiopian Plateau Catalogue//;​ //The AfricaArray Eastern Africa Seismic experiment//​). An up-to-date earthquake catalogue for Sub-Saharan Africa with homogenous magnitude representation (MW) was obtained by augmenting available global catalogues (e.g. //​ISC-Reviewed//,​ //​ISC-GEM//,​ //GCMT//, //GEM Historical Catalogue//​) with information from local agencies and regional projects, particularly from AfricaArray temporary deployments (//The Tanzanian Broadband Seismic Experiment//;​ //The Ethiopian Plateau Catalogue//;​ //The AfricaArray Eastern Africa Seismic experiment//​).
  
-The homogeneous SSA-GEM catalogue was then purged from fore- and aftershock sequences and seismic swarms, using the declustering algorithm introduced by Gardner and Knopoff (1974). The declustered SSA-GEM catalogue consists of 7,259 events out of the original 29,803 in the magnitude range 3 ≤ MW ≤ 7.53.+The homogeneous SSA-GEM catalogue was then purged from fore- and aftershock sequences and seismic swarms, using the declustering algorithm introduced by Gardner and Knopoff (1974). The declustered SSA-GEM catalogue consists of 7,259 events out of the original 29,803 in the magnitude range 3 ≤ Mw ≤ 7.53.
  
 {{ :​ssa_cat.png?​400 |}} {{ :​ssa_cat.png?​400 |}}
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 ===== Seismicity Parameters ===== ===== Seismicity Parameters =====
  
-|<80%>| +Seismicity in each area source is assumed to follow a double truncated Gutenberg-Richter magnitude occurrence relation (or magnitude-frequency distribution,​ MFD). Lower truncation is arbitrarily assigned to Mw 4.5 
-| **Group** ​ | **Source** | **//a//-value** | **//b//-value** | **Mw-max** |+ 
 +Gutenberg-Richter b-values have been calibrated for the whole catalogue and independently for each source group. Conversely, occurrence rates (a-values) have been calculated separately for each source zone by imposing the previously calibrated b-values. 
 + 
 +A different maximum magnitude (Mw-Max) estimate is derived independently for each source group as the largest observed event plus an arbitrary - although quite conservative - increment of 0.5 magnitude units. 
 + 
 +|<60%>| 
 +| **Group** ​ | **Source** | **a-Value** | **b-Value** | **Mw-Max** |
 | 1      | 2      | 4.83    | 1.02    | 7.2   | | 1      | 2      | 4.83    | 1.02    | 7.2   |
 |        | 3      | 5.38    |         ​| ​      | |        | 3      | 5.38    |         ​| ​      |
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 The figures below represent hazard maps for peak ground acceleration,​ for 10% of exceedance in 50 years and different spectral periods, calculated using the OpenQuake-engine. The figures below represent hazard maps for peak ground acceleration,​ for 10% of exceedance in 50 years and different spectral periods, calculated using the OpenQuake-engine.
  
-  - **PGA** {{ :​ssa_hazmap_mean_poe0.1_pga.png?​400 |}} +  - **Acceleration @ PGA** {{ :​ssa_hazmap_mean_poe0.1_pga.png?​400 |}} 
-  - **0.2s** {{ :​ssa_hazmap_mean_poe0.1_sa_0.2_.png?​400 |}}+  - **Acceleration @ 0.2s** {{ :​ssa_hazmap_mean_poe0.1_sa_0.2_.png?400 |}} 
 +  - **Acceleration @ 1s** {{ :​ssa_hazmap_mean_poe0.1_sa_1.0_.png?400 |}}
  
  
  • ssahara2016.txt
  • Last modified: 2017/11/23 11:06
  • by Valerio Poggi