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ssahara2016 [2017/06/13 14:32]
Valerio Poggi [Seismicity Parameters]
ssahara2016 [2017/11/23 11:06] (current)
Valerio Poggi [Download The OpenQuake-engine Input Model]
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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 =====
 +
 +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
 +
 +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%>​| |<​60%>​|
-| **Group** ​ | **Source** | **a-value** | **b-value** | **M-max** |+| **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    |         ​| ​      |
 | 2      | 1      | 4.48    | 0.95    | 7.5   | | 2      | 1      | 4.48    | 0.95    | 7.5   |
-:::    ​| 4      | 4.18    |         ​| ​      | +       | 4      | 4.18    |         ​| ​      | 
-:::    ​| 22     | 3.70    |         ​| ​      |+       | 22     | 3.70    |         ​| ​      |
 | 3      | 7      | 4.00    | 1.02    | 6.9   | | 3      | 7      | 4.00    | 1.02    | 6.9   |
-:::    ​| 7.1    | 4.23    |         ​| ​      | +       | 7.1    | 4.23    |         ​| ​      | 
-:::    ​| 14     | 4.34    |         ​| ​      | +       | 14     | 4.34    |         ​| ​      | 
-:::    ​| 20     | 3.31    |         ​| ​      |+       | 20     | 3.31    |         ​| ​      |
 | 4      | 5      | 4.22    | 1.02    | 7.9   | | 4      | 5      | 4.22    | 1.02    | 7.9   |
-:::    ​| 6      | 4.89    |         ​| ​      | +       | 6      | 4.89    |         ​| ​      | 
-:::    ​| 8      | 4.84    |         ​| ​      | +       | 8      | 4.84    |         ​| ​      | 
-:::    ​| 9      | 4.93    |         ​| ​      | +       | 9      | 4.93    |         ​| ​      | 
-:::    ​| 18     | 4.40    |         ​| ​      |+       | 18     | 4.40    |         ​| ​      |
 | 5      | 10     | 3.90    | 0.99    | 6.9   | | 5      | 10     | 3.90    | 0.99    | 6.9   |
-:::    ​| 10.1   | 3.92    |         ​| ​      | +       | 10.1   | 3.92    |         ​| ​      | 
-:::    ​| 11     | 3.51    |         ​| ​      | +       | 11     | 3.51    |         ​| ​      | 
-:::    ​| 11.1   | 3.93    |         ​| ​      | +       | 11.1   | 3.93    |         ​| ​      | 
-:::    ​| 12     | 4.05    |         ​| ​      | +       | 12     | 4.05    |         ​| ​      | 
-:::    ​| 12.1   | 4.13    |         ​| ​      | +       | 12.1   | 4.13    |         ​| ​      | 
-:::    ​| 13     | 4.08    |         ​| ​      | +       | 13     | 4.08    |         ​| ​      | 
-:::    ​| 13.1   | 3.99    |         ​| ​      |+       | 13.1   | 3.99    |         ​| ​      |
 | 6      | 15     | 5.31    | 1.16    | 7.4   | | 6      | 15     | 5.31    | 1.16    | 7.4   |
-:::    ​| 16     | 5.45    |         ​| ​      | +       | 16     | 5.45    |         ​| ​      | 
-:::    ​| 17     | 4.77    |         ​| ​      |+       | 17     | 4.77    |         ​| ​      |
  
 ===== The Ground Motion Model ===== ===== The Ground Motion Model =====
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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 |}}
  
  
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 ===== Download The OpenQuake-engine Input Model ===== ===== Download The OpenQuake-engine Input Model =====
  
-The OpenQuake-engine input model (NRML format) ​can be downloaded at the link provided below Please read the license and disclaimer attached to the model. ​                                                                                                                                                                                                                                      ​+GEM platform is presently under reorganisation. ​The OpenQuake-engine input files (NRML format) ​for the Sub-Saharan Africa ​model will be released publicly as soon as in our possibilities.
  
-[[https://​platform.openquake.org/​documents/​91 | Download]]+For more information,​ please contact <​hazard@globalquakemodel.org>
  • ssahara2016.1497357127.txt.gz
  • Last modified: 2017/06/13 14:32
  • by Valerio Poggi