Uniform Hazard Spectra

Discover models that provide uniform hazard spectra

A uniform hazard spectrum gives the spectral acceleration over a range of periods, all with the same probability of exceedance within a given time span. Uniform hazard spectra are available through the EFEHR REST API under the base URL https://efehr-services.ethz.ch/hazard/api/v1. All endpoints use HTTP GET and return JSON by default; add format=nrml to receive NRML instead. Data are published under CC BY 4.0 (DOI 10.12686/a15).

The steps below find the models providing spectra at your site, narrow down the available options (intensity measure type, probability of exceedance, soil type, aggregation) and then retrieve the spectrum. The examples use Basel (47.5° N, 7.6° E) and the European Seismic Hazard Model 2020 (ESHM20, model id 81), with an annual probability of exceedance of 0.002103 (equivalent to 10% in 50 years). Long lists in the response examples are shortened with "…". The complete, interactive reference is available at efehr-services.ethz.ch/hazard/api/docs.

Discovering models that provide uniform hazard spectra

User query Which hazard models provide uniform hazard spectra for the site of my interest?
Request format /v1/spectra/models?lat=[latitude]&lon=[longitude]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra/models?lat=47.5&lon=7.6
Response example 
{
  "models": [
    {
      "id": 77,
      "name": "Swiss Hazard Model 2015 (SUIhaz15)"
    },
    {
      "id": 81,
      "name": "European Seismic hazard Model 2020 (ESHM20)"
    }
  ],
  "count": 2
}

Selecting spectral ground motion types

User query For which intensity measure types (IMT) are response spectra available from a selected model at my site of interest? Spectra are typically provided for spectral acceleration (SA).
Request format /v1/spectra/imts?lat=[latitude]&lon=[longitude]&modelid=[modelid]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
  • modelid (required): model identifier, from the model list
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra/imts?lat=47.5&lon=7.6&modelid=81
Response example 
{
  "imts": [
    {
      "code": "SA",
      "name": "SA",
      "unit_type": "g",
      "unit_description": "gravity, 1g = 980.5 cm/s/s"
    }
  ]
}

Exploring probabilities of exceedance and time spans

User query For which probabilities of exceedance and time spans are response spectra available from a selected model and IMT at my site of interest? ESHM20 provides annual probabilities, which correspond to the usual 50-year values: 0.00019999 (1% in 50 years, return period about 5000 years), 0.000399999 (2%, about 2500 years), 0.0010249 (5%, about 975 years), 0.002103 (10%, about 475 years), 0.00989 (39%, about 100 years) and 0.02 (63%, about 50 years).
Request format /v1/spectra/poe?lat=[latitude]&lon=[longitude]&modelid=[modelid]&imt=[IMT]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
  • modelid (required): model identifier, from the model list
  • imt (required): spectral intensity measure type, e.g. SA (spectral acceleration)
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra/poe?lat=47.5&lon=7.6&modelid=81&imt=SA
Response example 
{
  "poe_values": [
    {
      "probability": 0.00019999,
      "years": 1
    },
    {
      "probability": 0.000399999,
      "years": 1
    },
    {
      "probability": 0.0010249,
      "years": 1
    },
    {
      "probability": 0.002103,
      "years": 1
    },
    {
      "probability": 0.00989,
      "years": 1
    },
    {
      "probability": 0.02,
      "years": 1
    }
  ]
}

For which site classes do spectra apply?

User query For which soil classes or surface geology conditions are uniform hazard spectra available from the model of my interest, for the selected IMT and probability of exceedance, at my site of interest?
Request format /v1/spectra/soiltypes?lat=[latitude]&lon=[longitude]&modelid=[modelid]&imt=[IMT]&poe=[poe]&timespan=[years]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
  • modelid (required): model identifier, from the model list
  • imt (required): spectral intensity measure type, e.g. SA (spectral acceleration)
  • poe (required): probability of exceedance, 0 to 1 (e.g. 0.002103)
  • timespan (required): investigation time in years (e.g. 1 for annual probabilities)
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra/soiltypes?lat=47.5&lon=7.6&modelid=81&imt=SA&poe=0.002103&timespan=1
Response example 
{
  "soil_types": [
    {
      "code": "rock_vs30_800ms-1",
      "name": "rock_vs30_800ms-1"
    }
  ]
}

Aggregation of hazard spectra from logic tree models

User query Given a model, an IMT, a probability of exceedance and a soil type, how was the uniform hazard spectrum of a multi-branch logic tree model aggregated? Answers are the arithmetic mean or quantiles (ordinal aggregation with levels from 0 to 1).
Request format /v1/spectra/fractiles?lat=[latitude]&lon=[longitude]&modelid=[modelid]&imt=[IMT]&poe=[poe]&timespan=[years]&soiltype=[soiltype]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
  • modelid (required): model identifier, from the model list
  • imt (required): spectral intensity measure type, e.g. SA (spectral acceleration)
  • poe (required): probability of exceedance, 0 to 1 (e.g. 0.002103)
  • timespan (required): investigation time in years (e.g. 1 for annual probabilities)
  • soiltype (optional): soil type code
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra/fractiles?lat=47.5&lon=7.6&modelid=81&imt=SA&poe=0.002103&timespan=1&soiltype=rock_vs30_800ms-1
Response example 
{
  "fractiles": [
    {
      "aggregation_type": "arithmetic",
      "aggregation_level": 0.5
    },
    {
      "aggregation_type": "ordinal",
      "aggregation_level": 0.05
    },
    {
      "aggregation_type": "ordinal",
      "aggregation_level": 0.16
    },
    {
      "aggregation_type": "ordinal",
      "aggregation_level": 0.5
    },
    {
      "aggregation_type": "ordinal",
      "aggregation_level": 0.84
    },
    {
      "aggregation_type": "ordinal",
      "aggregation_level": 0.95
    }
  ]
}

Retrieving a uniform hazard spectrum

User query Given all previously selected parameters, what is the uniform hazard spectrum at my site of interest?
Request format /v1/spectra?lat=[latitude]&lon=[longitude]&modelid=[modelid]&imt=[IMT]&poe=[poe]&timespan=[years]&soiltype=[soiltype]&aggregationtype=[arithmetic | ordinal]&aggregationlevel=[0…1]
Parameters
  • lat (required): latitude, −90 to 90
  • lon (required): longitude, −180 to 180
  • modelid (required): model identifier, from the model list
  • imt (optional): spectral intensity measure type, default SA
  • poe (required): probability of exceedance, 0 to 1 (e.g. 0.002103)
  • timespan (required): investigation time in years (e.g. 1 for annual probabilities)
  • soiltype (optional): soil type code
  • aggregationtype (optional): arithmetic (mean) or ordinal (quantile)
  • aggregationlevel (optional): aggregation level, 0 to 1 (e.g. 0.5 for the median)
  • format (optional): json (default) or nrml
Request example https://efehr-services.ethz.ch/hazard/api/v1/spectra?lat=47.5&lon=7.6&modelid=81&imt=SA&poe=0.002103&timespan=1&soiltype=rock_vs30_800ms-1&aggregationtype=ordinal&aggregationlevel=0.16
Response example 
{
  "spectra": [
    {
      "lon": 7.5821339,
      "lat": 47.5,
      "model_id": 81,
      "model_name": "European Seismic hazard Model 2020 (ESHM20)",
      "imt": "SA",
      "poe": 0.002103,
      "timespan": 1,
      "soil_type": "rock_vs30_800ms-1",
      "aggregation_type": "ordinal",
      "aggregation_level": 0.16,
      "damping": null,
      "points": [
        {
          "period": 0.0,
          "acceleration": 0.040773556
        },
        {
          "period": 0.05,
          "acceleration": 0.056854393
        },
        {
          "period": 0.1,
          "acceleration": 0.08881868
        },
        {
          "period": 0.15,
          "acceleration": 0.10227363
        },
        {
          "period": 0.2,
          "acceleration": 0.1016133
        },
        {
          "period": 0.25,
          "acceleration": 0.092453286
        },
        {
          "period": 0.3,
          "acceleration": 0.08032928
        },
        {
          "period": 0.35,
          "acceleration": 0.070245504
        },
        {
          "period": 0.4,
          "acceleration": 0.0620625
        },
        {
          "period": 0.5,
          "acceleration": 0.049622025
        },
        {
          "period": 0.6,
          "acceleration": 0.041263234
        },
        {
          "period": 0.75,
          "acceleration": 0.031814687
        },
        {
          "period": 1.0,
          "acceleration": 0.023731295
        },
        {
          "period": 2.0,
          "acceleration": 0.009335869
        },
        {
          "period": 3.0,
          "acceleration": 0.0052169817
        },
        {
          "period": 4.0,
          "acceleration": 0.0034016648
        },
        {
          "period": 5.0,
          "acceleration": 0.0028997352
        }
      ]
    }
  ],
  "metadata": {
    "source": "EFEHR Services FastAPI",
    "timestamp": null
  }
}
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