Earthquakes
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Geological hazards include events such earthquakes, landslides and volcanos and there are a range of maps and products that can be produced before and after the event or events. Often when there is one event there may be secondary hazards and events. For example, after an earthquake there may be aftershocks, a tsunami, liquefaction or landslides.
Maps produced during a humanitarian response to earthquakes, visualising the seismic data and any data that may forecast the extent of physical damage and potentially act as a proxy for humanitarian impact. It may be combined with other thematic layers, notably with baseline population data to enable a rapid/early analysis of the population potentially affected.
Both
Situational.
At an early stage after the occurrence of a major earthquake with the potential to create damage and casualties. The necessary data will invariably be available within hours of the initial earthquake. Data and maps may be updated following aftershocks or to add additional analysis layers, including for example assessed landslide risk zones, vulnerable infrastructure (e.g. dams), or population baselines.
All responders, but particularly those operating across the wider affected area and including actors working on assessment processes and response planning and coordination.
The map will provide context to the potential scope and scale of earthquake. It shows them the location of the epicentre (and aftershocks) and the intensity in different areas. When this is shown with population data it will also give an indication of potentially where the most affected people will be. It will inform them of where potential search and rescue activity might be required.
Initial data, typically from United States Geological Survey (USGS) Earthquake alerts, will give basic indicators including the magnitude and location of the epicentre of the initial event and any aftershocks. This point data should be placed on the map first. It is not good practice to buffer circular rings around the epicentre as this may imply a spatially regular fall-off of damage which is very unlikely to reflect reality. As a large earthquake is “more appropriately described as a slip over a larger fault area” (USGS, see below), single points are poor representations of large earthquakes, so a map showing zones of ‘shake intensity’ provides more useful information. Analysed shake intensity zone data should be obtained mapped as soon as possible. Because this is modelled predictively rather and not ground truthed, it should be appropriately explained and have a caveat on maps. A suitable base map will normally include terrain and any available data on population distribution or population places.
Geophysical data is usually obtained from United States Geological Survey or others. This may include locations of reported epicentres of primary and aftershocks (as points), and modelled shake intensity (as polygons).
Data on predicted or actual landslides from various providers; but be cautious of the methods used to derive these as they may not be reliable.
Analysed satellite imagery to identify building damage; but be cautious because analysis methods may not have been standardised or reliable, and take special care to identify areas that have not been analysed.
These are maps depicting the hazards and impacts of landslides or other mass movements such as snow avalanches.
Usually operational.
Situational.
When landslides pose the main or a secondary humanitarian hazard, particularly in association with earthquakes or storm events (particularly after very heavy rainfall). Maps may be produced to identify areas vulnerable to landslides in order to identify at risk communities, or to prioritise on-the-ground or aerial damage assessments. Landslides may also be mapped to identify barriers to access to disaster-affected areas.
All responders, but particularly those working on assessment processes and response planning and coordination. Also, when relevant, logistics planning actors.
Landslides can have a direct impact on communities, and can also block access to large areas of land. Maps showing known/confirmed landslides may be valuable as proxy indicators of likely damage and needs after an earthquake or storm event. Predictive mapping should be used only with caution.
Predictive mapping of landslides may use spatial variables such as earthquake shake intensity, slope angles and cumulative rainfall statistics.
Data on actual landslides can be reliably obtained from ground level, aerial or satellite remote sensing. If these are included on maps, then any areas not analysed should be clearly identified to avoid "no data = no impact" confusions.
In the case of earthquakes: modelled shake intensity (as polygons).
In the case of storms events: cumulative rainfall data – typically from national or regional meteorological agencies.
Terrain data allowing analysis of average slope angles.
Reported landslide locations (points or polygons) derived from ground survey, aerial or satellite imagery.
Maps relating to volcanic activity may show pre-existing lava and pyroclastic flows, vents and craters. They may also show other associated hazards such as new lava flows, volcanic gas, lahars, jökulhlaups and pyroclastic flows. Decision-makers will be looking to identify possible evacuation routes from these maps.
Both
Basemap and situational.
Pre-existing geological maps may already exist and these can be used early on. As the situational data arrives it is important that the maps are updated. This is particularly the case where volcanic gas and ash clouds are present and there is wind and rain in the area, which will influence which direction the ash will carry and how much is in the air.
Civil defence and anyone involved with evacuation.
Decision-makers are going to be interested in identifying evacuation routes and safe zones. Basemaps may show pre-existing lava and pyroclastic flows, vents and craters. Volcanic hazards that may need to be mapped or may influence decision-making include:
Lava flows: molten rock that is expelled during a volcanic eruption and moves downhill.
Volcanic gas: this will be released by a volcano typically as water vapour, but also as carbon dioxide, carbon monoxide, sulphur oxides, hydrogen sulfide, chlorine and fluorine. Most of the time volcanic gases are noxious, but they can cause mass fatalities.
Lahars: these are particular types of mud flows containing a mixture of pyroclastic materials, rocky debris and water. These can occur as a result of heavy rainfall, the rapid draining of a crater lake or melting ice. These flows can be highly damaging. When the flows stop they can become as solid as concrete.
Jökulhlaups: this is a kind of glacial outburst flood associated with geothermal activity under a glacier.
Pyroclastic flows: a fast moving current of hot gas and rock that flows down and away from the volcano.
Create distance buffers around the volcano. These can then be used to identify villages and communities possibly within reach of gas and ash clouds. Distance products depicting the spread of gas and ash can be produced by using wind direction and speed.
Geological mapping showing vents and other hazards.
Ash and gas cloud.
Wind direction and speed.
Liquefaction will typically (but not exclusively) occur as a result of an earthquake and can cause significant destruction. Maps on liquefaction may show either areas at risk to it through complex modelling or post event areas and the damage caused by liquefaction.
Both
Baseline and situational.
Liquefaction modelling will occur before the event as a preparedness activity by a government, scientific or engineering organisation. Post event, mapping may happen as a result of field assessments or remote sensing analysis.
Anyone involved with planning will be interested in modelling maps and those involved with response will be interested in post disaster mapping.
Modelled maps will be used by planners and officials to understand the areas and populations that may be exposed and prone to liquefaction. If in the event of liquefaction responders, particularly the urban search and rescue teams, will be wanting to understand where liquefaction has occurred so that they can facilitate any rescues.
liquefaction modelling is a complex methodology and will required a range of datasets including rock and soil type, hydrology, buildings and seismological. Post disaster mapping should show the extent of the liquefaction, any damage to buildings and general infrastructure and also the population that has been affected. Satellite and aerial photography can be used to identify those areas, as well as field assessments.
Modelled liquefaction exposure
Pre and post disaster imagery to compare the areas before and after
Building and landuse
Population
Infrastructure
Maps produced during a humanitarian response to destructive tsunami, usually arising from offshore earthquakes. This section describes mapping the specific impacts of the tsunami, rather than the trigger earthquake, which may itself have direct effects on land.
Both
Situational.
Usually early on in the response, to map impact information that can then highlight priorities for a life-saving response, and to focus in-field damage and needs assessment on areas most likely to be affected.
All responders, but particularly those operating across the wider affected area, including actors working on assessment processes and response planning and coordination, and on logistics planning.
Tsunamis cause humanitarian impacts through their direct effects (coastal flooding with little or no warning), and indirectly they may hamper a response to the wider impacts of an earthquake, for example by impeding access. Any impact close to the coast is likely to be devastating, and create multi-faceted needs in densely populated coastal zones. Where primary transport links have been severed, e.g. coastal roads, mapping is likely to be an important tool for planning and coordinating logistical access to affected communities.
While the extent of inundation will vary along a coast hit by a tsunami, it can be assumed that communities close to the coast, even if not flooded, will see affected people seeking refuge. Therefore, mapping of communities, with population figures of those living within the coastal zone will be valuable for needs assessment.
The following data types may be available from national or regional meteorological agencies:
Modelled data on tsunami propagation, if available. However, be aware that local variations in coastal morphology will greatly vary the wave impact location by location.
Settlement data for coastal districts.
Road data, including if possible locations of bridges over coastal inlets.
Search and rescue maps are often produced during a humanitarian response to earthquakes, focusing on the hazards and impacts that typically characterise these emergencies. They should facilitate a timely response to earthquake disasters, focusing on anticipated hazards such as aftershocks, and the impacts of this type of event. Maps may be produced to coordinate urban search and rescue (USAR) efforts, to visualise access to affected areas, to analyse patterns of structural damage and assessed needs, or to plan a humanitarian response across multiple sectors.
Both
Situational.
Usually early on in the response, to provide initial predictive or actual impact information that can then highlight priorities for life-saving responses including urban search and rescue, and to focus in-field damage and needs assessment on areas most likely to be affected.
All responders, but particularly those operating across the wider affected area, and including actors working on assessment processes and response planning and coordination.
Earthquakes often affect very wide areas, much of which may be rendered inaccessible by the disaster. Initial response decisions including resource mobilisation should be taken in light of what can be inferred from predictors of physical damage, including geophysical mapping. However, such predictors should be used with caution, and should be triangulated as soon as possible with mapping of primary data such as field assessment reports.
Operationally, search and rescue teams require rapid detailed maps of collapsed site locations and search sector boundaries, as well as hospital locations and status, base of operations and other resources.
It is important to get street level mapping produced as early as possible, and the inclusion of satellite or aerial imagery may also help responders identify key features on the ground.
When producing a sector map use linear features that are easily identifiable on the ground post- earthquake, such as broad roads or rivers. Maps should include building outlines where possible or give an indication of building and population density. The greater the density the smaller the sectors should be, as these will most likely take the longest to search. Initial sectors may be quite large to begin with, but smaller sub-sectors may be created. Each sector or sub-sector should be given a unique ID so that rescue teams can identify them more easily. Maps should include a table showing the sector’s ID, the team that is working the area, and the team type (heavy, medium or light).
Roads
Building Type
Place names
Points of Interest
Hospitals
Analysed satellite imagery to identify building damage; but be cautious because analysis methods may not have been standardised or reliable, and take special care to identify areas that have not been analysed.
