The Global Centre for Risk and Innovation (GCRI)
Earthquakes, tsunamis, volcanic eruptions, landslides and subsidence arise from the solid Earth and give little or no warning. Their timing cannot be predicted, but where and how strongly they can occur can be assessed and built for. This page sets out how geohazards arise, how hazard is estimated probabilistically, and what evidence serves the agencies that set building codes, plan land use and monitor active systems.
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Earthquakes and geohazards are hazards from the solid Earth, including earthquakes, tsunamis, volcanic eruptions, landslides and subsidence. Their timing cannot be predicted, but probabilistic hazard analysis estimates how likely given shaking is over a period. Building codes, land-use plans and observatory monitoring rest on that evidence.
The working screen behind this subject: its structure, terms and states. Names are placeholders and values illustrative.
Earthquakes and geohazards · River delta · Return period set
hydraulic model · placeholder
| 1-in-10 | 14 | 0.9 |
| 1-in-100 | 37 | 1.4 |
| 1-in-1000 | 63 | 2.1 |
Earthquakes, volcanoes and related hazards. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
Tectonic plates move steadily, and faults lock until stress exceeds their strength. The sudden slip radiates seismic waves whose shaking depends on magnitude, distance, depth and local ground.
Soft sediments amplify and lengthen shaking, and loose saturated soils can liquefy. Two buildings at the same distance from an earthquake can experience very different motion.
Earthquakes, submarine landslides and volcanic collapses displace water, sending waves across ocean basins. Near-source coasts may have only minutes before arrival.
Strong shaking and heavy rain trigger landslides, which can dam rivers and later release floods. Volcanic ash disrupts aviation and agriculture far from the vent.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Seismic hazard | The probability of a level of ground shaking being exceeded at a site in a given time. |
| Liquefaction | Loss of strength in saturated loose soil during shaking, causing it to behave like a liquid. |
| Moment magnitude | A measure of earthquake size based on the fault area, slip and rock rigidity. |
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Earthquake magnitude | moment magnitude | per event | Seismic network catalogues | OBSERVED |
| Peak ground acceleration | fraction of gravity | per event | Strong-motion stations and ShakeMap estimates | OBSERVED |
| Macroseismic intensity | intensity scale level | per event | Felt reports and intensity models | ESTIMATED |
| Seismic hazard at a return period | peak ground acceleration with a stated exceedance probability | per model release | Probabilistic seismic hazard models | MODELLED |
| Landslide susceptibility | susceptibility class | per assessment | Susceptibility models | MODELLED |
| Ground deformation rate | millimetres per year | per acquisition series | Satellite radar interferometry | OBSERVED |
| Volcanic alert level | alert level on the observatory's scale | as issued | Volcano observatories | OFFICIAL |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| USGS ANSS Comprehensive Earthquake Catalog (ComCat) | Global earthquake locations, magnitudes and ShakeMaps | Public domain, US government data |
| International Seismological Centre Bulletin | Reviewed global earthquake parameters | Free with citation, ISC terms (to check) |
| Global Earthquake Model (GEM) global hazard and risk maps | Probabilistic seismic hazard and risk mosaics | CC BY-NC-SA 4.0 for the public maps (to check) |
| Smithsonian Global Volcanism Program | Volcano and eruption records | Free with citation, terms to check |
| NASA Global Landslide Catalog | Rainfall-triggered landslide events | Open, NASA data policy |
| NOAA NCEI Global Historical Tsunami Database | Tsunami events and run-up observations | Public domain, US government data |
| Copernicus Sentinel-1 radar data | Inputs for ground deformation and landslide monitoring | Free and open, Copernicus terms |
Climate and Hazards prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Building code committees | Which seismic design values apply in each zone | Hazard models with exceedance probabilities and site effects |
| Geological surveys and volcano observatories | Which areas need monitoring, mapping or alert changes | Deformation evidence; catalogues; susceptibility maps |
| Spatial planning authorities | Where to restrict building on unstable or liquefiable ground | Susceptibility and site condition evidence |
| Tsunami warning centres and coastal authorities | Which coasts need evacuation routes and signs | Tsunami history and inundation scenarios |
Geohazard questions are about where, how big and with what effects.
Earthquakes release strain accumulated as tectonic plates move. The energy radiates as seismic waves whose effect at the surface depends on distance, depth and local ground conditions; soft sediments can amplify shaking and saturated soils can liquefy. Large earthquakes are followed by aftershocks, and some trigger landslides and tsunamis.
Volcanic hazards include ash fall, pyroclastic flows, lava, gases and mudflows called lahars, which can travel far down valleys. Landslides occur when slopes fail under gravity, often triggered by heavy rain, earthquakes, snowmelt or human changes to slopes; their rainfall triggers link them to climate. Tsunamis travel across ocean basins at high speed, so warning time depends on distance from the source.
| Method or data | What it shows | Limits |
|---|---|---|
| Seismic networks and catalogues | Where and how often earthquakes occur | Catalogues are short relative to large-earthquake recurrence |
| Probabilistic seismic hazard analysis | The likelihood of exceeding given ground-shaking levels | Depends on fault models and ground-motion models with large uncertainty |
| Geodesy, including satellite radar and positioning | Ground deformation and strain accumulation | Shows strain, not when it will be released |
| Volcano monitoring | Seismicity, gas and deformation signalling unrest | Unrest does not always lead to eruption |
| Landslide susceptibility mapping | Where slopes are prone to fail | Timing remains hard to predict |
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.