The 2010 USGS Seismic Hazard Model for South America
The 2010 USGS seismic hazard model for South America is described in Petersen et al. (2010) (see also the USGS Website). We provide here a short description of the OpenQuake-engine implementation of the model.
Basic Datasets
Earthquake catalogue
The earthquake catalogue was compiled using instrumentally recorded earthquakes from four global catalogues:
- The Centennial catalogue (Engdahl and Villaseñor, 2002) link;
- The EHB catalogue (Engdahl et al., 1998) link;
- The USGS/NEIC catalogue (http://neic.usgs.gov) and;
- The ISC catalogue (http://www.isc.ac.uk).
The Seismic Source Model
The seismic source model employs different seismic source typologies to model seismicity occurring in different tectonic settings. Gridded seismicity is used to model both spatially variable seismicity as well as zones of uniform seismicity. Fault sources are instead used to model shallow crustal faults and large subduction interface faults.
Gridded seismicity models are implemented as collections of point sources (following the NRML pointSource definition). Crustal and subduction interface faults are instead modeled as simple (NRML simpleFaultSource) and complex fault sources (NRML complexFaultSource) when associated to a Gutenberg-Richter magnitude-frequency distribution, and as characteristic fault sources (NRML characteristicFaultSource) when associated to a Characteristic model.
The entire source model can be divided into a number of sub-models:
- Active shallow crust gridded seismicity
- Subduction intraslab gridded seismicity
- Stable continental crust gridded seismicity
- Active shallow crust faults
- Stable continental crust faults
- Subduction interface faults
The map below depicts the annual occurrence rate per source (between minimum and maximum magnitudes) for the different source models included in the hazard model.Click the show map layers icon to view different source models and base layer maps.
operating instructions
Various functions are available as part of the map.
mouse/touch operation
- moving by grabbing the map with a mouse-click you can move the map around
- overview map using the + button in the bottom right of the map you can expand an overview map
- zooming in and out using the + and - buttons in the top left of the map you can obtain more or less detail in the map
- switching themes or maps clicking on the ≡ icon on the right-hand side of the map you can view and select available maps and themes
- retrieving information the map may contain elements that contain more information, by clicking these a popup will show this information
- fullscreen display using the ✈ button the map can be maximized to fullscreen display, use the ✕ button to return to page display.
keyboard operation
Keyboard operation becomes available after activating the map using the tab key (the map will show a focus indicator ring).
- moving using the arrow keys you can move the map
- overview map using the + button in the bottom right of the map you can expand an overview map
- zooming in and out using the + and - buttons in the top left of the map or by using the + and - keys you can obtain more or less detail in the map
- switching themes or maps clicking on the ≡ icon on the right-hand side of the map you can view and select available maps and themes
- retrieving information the map may contain elements that contain more information, using the i key you can activate a cursor that may be moved using the arrow keys, pressing the enter will execute an information retrieval. press the i or the escape key to return to navigation mode
- fullscreen display using the ✈ button the map can be maximized to fullscreen display, use the ✕ button to return to page display.
It's possible that some of the functions or buttons describe above have been disabled by the page author or the administrator
(number of events / year)
- < 1e-6
- 1e-6 - 1e-5
- 1e-5 - 1e-4
- 1e-4 - 1e-3
- 1e-3 - 1e-2
- 1e-2 - 1e-1
- 1e-1 - 1
- 1 - 10
- >= 10
The Ground Motion Model
The ground motion model distinguishes between four main tectonic regions:
- Active Shallow Crust
- Stable Continental Crust
- Subduction Interface
- Subduction Intraslab
For each tectonic region, various GMPEs are used to account for epistemic uncertainties.
| Active Shallow Crust | Weight |
| Boore and Atkinson 2008 | 0.333 |
| Campbell and Bozorgnia 2008 | 0.333 |
| Chiou and Youngs 2008 | 0.333 |
| Stable Continental Crust | Weight |
| Toro et. al. 1997 | 0.25 |
| Frankel et. al. 1996 | 0.125 |
| Campbell 2003 | 0.125 |
| Atkinson and Boore 2006 (140 bar stress drop) | 0.125 |
| Atkinson and Boore 2006 (200 bar stress drop) | 0.125 |
| Tavakoli and Pezeshk 2005 | 0.125 |
| Silva et. al. 2002 | 0.125 |
| Subduction Interface | Weight |
| Zhao et. al. 2006 | 0.5 |
| Atkinson and Boore 2003 | 0.25 |
| Youngs et. al. 1997 | 0.25 |
| Subduction Intraslab | Weight |
| Geomatrix 1993 | 0.5 |
| Atkinson and Boore 2003 (Global model) | 0.5 |
Reference site condition
The NEHRP B/C site condition is assumed to be the reference site conditions for the hazard model. This is equivalent to a Vs30 (shear wave velocity in the uppermost 30 meters) = 760 m/s. Almost all GMPEs utilized for active shallow crust and subduction interface accept Vs30 as prediction variable. The remaining GMPEs are used with coefficients corrected for the B/C site conditions. |
Hazard Results
Hazard Maps
The figures below represent hazard maps for peak ground acceleration, corresponding to 10% and 2% probabilities of exceedance in 50 years, computed with the OpenQuake-engine.
References
- Petersen, M., Harmsen, S., Haller, K., Mueller, C., Luco, N., Hayes, G., Dewey, J. and Rukstales, K. (2010), Preliminary Seismic Hazard Model for South America, in LA SISMOLOGÍA EN SUDAMÉRICA Y LOS MECANISMOS DE PREVENCIÓN Y MITIGACIÓN DEL PELIGRO Y RIESGO SÍSMICO, Daniel Huaco Editor, Lima, Peru. Link
Model summary table
This table summarises the main characteristics of the original implementation of this model
| 1 | Datasets availability | |
|---|---|---|
| 1.1 | Earthquake catalogue | Not available |
| 1.2 | Geological database | Not available |
| 1.3 | Strong-motion database | Not available |
| 1.4 | Site characterization database | Not available |
| Notes | ||
| 2 | Methodology for model development | |
| 2.1 | Scientific participation (SSHAC levels) and review process | Level 2 |
| 2.2 | Documentation describing model preparation | Not available |
| 2.3 | Codes used for model preparation | Partially available |
| Notes | ||
| 3 | PSHA input model | |
| 3.1 | Seismic Source Model | |
| 3.1.1 | Area sources | Not included |
| 3.1.2 | Grid sources | to model distributed seismicity in the shallow active crust and the inslab seismicity |
| 3.1.3 | Crustal faults | Included |
| 3.1.4 | Subduction faults | the subduction interface sources are modelled as faults |
| 3.1.5 | Non-parametric ruptures | Not included |
| 3.1.6 | Magnitude-area scaling relationships | Not explicit defined in Petersen et al. (2010) |
| 3.2 | Ground Motion Model | |
| 3.2.0 | Tectonic regionalisation | Not included |
| 3.2.1 | Models for active shallow seismicity | Included |
| 3.2.2 | Models for subduction interface | Included |
| 3.2.3 | Models for subduction intraslab | Included |
| 3.2.4 | Models for stable continental regions | Included |
| 3.2.5 | Models for deep non-subduction sources | Not included |
| 3.2.6 | Models for volcanic areas | Not included |
| 3.3 | Site Response Model | |
| 3.3.1 | Based on GMPEs | Yes, hazard is computed for a reference soil condition corresponding to NEHRP B/C boundary (Vs30=760 m/s) |
| 3.3.2 | Based on site-response analysis | No |
| 3.4 | Epistemic uncertainties | |
| 3.4.1 | Seismic Source Model | Not included |
| 3.4.2 | Ground Motion Model | Included using a logic tree (see the ground motion model section) |
| 3.4.3 | Site Response Model | Not included |
| Notes | ||
| 4 | Hazard Input Description | |
| 4.1 | Hazard input document | Not inlcuded |
| 4.2 | Input files | Not inlcuded |
| Notes | ||
| 5 | Calculation | |
| 5.1 | Software | Suite of Fortran codes developed by the USGS-NSHM group. |
| 5.2 | Results | |
| 5.2.1 | Hazard curves | Not directly available |
| 5.2.2 | Hazard maps | Not directly available |
| 5.2.3 | Uniform hazard spectra | Not directly available |
| 5.2.4 | Disaggregation | Not directly available |
| 5.2.5 | Stochastic event sets | Not considered |
| 5.2.6 | Ground motion fields | Not considered |
| Notes | ||