Radon potential is the ability of rocks and soils to produce radon. Radon is a colorless and odorless gas, a radioactive byproduct of radium. This gas becomes a human health concern when radon makes its way from the building ground into structures. If radon builds up to high concentrations in indoor air, radon and its decay products can get trapped in the lungs through inhalation exposure. Long-term exposure to high radon levels may lead to lung cancer in some people.

The only way to determine radon levels accurately in individual buildings is by making measurements of indoor air. All residences regardless of location should be tested for radon. For more information on radon, go to Radon Risk in Oregon, part of the Oregon Health Authority Radon Gas website.

Types and Sources of Radon Data
There are four sources of data for the radon potential map, listed in order of importance, starting with most important source data:

• Uranium host rock data (Mineral Information Layer for Oregon, release 2 [MILO-2]) [note: as of 2020, MILO-3 dataset is available];
• Indoor radon test results shared by test kit manufacturers with Oregon Health Authority (OHA);
• Aeroradiometric data from the National Uranium Resource Evaluation project (NURE);
• Statewide geologic mapping (Oregon Geology Data Compilation, release 6 [OGDC-6]).

Learn more about this layer: DOGAMI Open-File Report O-18-01, Radon potential in Oregon

Intended Use and Data Limitations
The resolution of the data is 1:100,000 scale. The information was meant not to predict indoor radon test results but to help agencies target their radon program activities and resources. It is the user’s responsibility to examine the actual data and understand how the data apply to radon potential. Use of the map data also requires knowledge of local conditions and the application of professional judgment and common sense. Other limitations apply to the underlying geodatabase that produced the radon layer data:

• The data do not show or predict absolute indoor radon levels in buildings. Those levels are estimates in terms of an average indoor radon potential for the area of the geologic polygon. Other factors that are not trivial contribute to elevated indoor radon hazard potential in specific buildings, measures of which were beyond the scope of the study that produced the radon layer map.
• A radon hazard level may only cover a fraction of the geologic polygon’s area. The user should evaluate an area with caution and should always examine the actual data to gain a better perspective.
• Localized areas of higher or lower radon potential are likely to exist within any given geology polygon, but their identification is not possible because of scale, sparse data, or a combination of both.
• Hazard classifications are approximate and so are the underlying mapped boundaries (i.e., geologic polygons).
• The sample set of indoor radon tests is relatively small with spatial variations in sample sizes. Both introduce varying degrees of uncertainty. Therefore, more widespread and focused radon testing along with detailed geologic mapping would inform future radon potential maps.

Floods are a common and widespread natural hazard in Oregon. Flooding typically results from large-scale weather systems generating prolonged rainfall and from “rain on snow” events that cause large amounts of snowmelt.

In Oregon, these conditions are most common from October through April when storms from the Pacific Ocean bring intense rainfall. Flooding can be aggravated when streams are altered by human activity, such as through channelization of streams or loss of wetlands. Wildfires can also increase the likelihood of flooding by removing vegetation and increasing rainfall runoff. Many types of flood hazards exist in Oregon, including riverine floods, flash floods (resulting from locally intense thunderstorms, ice jams and dam failures), coastal floods, channel migration and bank erosion, shallow area and urban flooding and playa flooding. Flood hazards can cause severe property damage and loss of life.

Effective FEMA Flood Data

The following FEMA datasets are periodically downloaded from the FEMA Flood Map Service Center to reflect the most recent effective flood data.

Floodway
The floodway, also known as the regulatory floodway, includes both the active channel of a stream and the adjacent floodplain area that must be kept free of development so that the 100-year flood discharge can pass through without increasing the elevation of the 100-year flood by more than a designated height.

100-Year Floodplain
The 100-year floodplain is a flood zone developed by statistical analyses of stream discharge data to define the 1%-annual-chance flood event. The recurrence interval is based on the probability that the given event will be equaled or exceeded in any given year. The resulting flood water surface is mapped on best available topographic data, ranging from lidar (most accurate) to USGS topographic maps (least accurate). There is a 26% chance that a “100-year flood” will occur during the next 30 years.

500-Year Floodplain
The 500-year floodplain is a flood zone developed by statistical analyses of stream discharge data to define the 0.2%-annual-chance flood event. The recurrence interval is based on the probability that the given event will be equaled or exceeded in any given year. The resulting flood water surface is mapped on best available topographic data, ranging from lidar (most accurate) to USGS topographic maps (least accurate). There is a 5-6% chance that a “500-year flood” will occur during the next 30 years.

More information: FEMA National Insurance Flood Program.

Non-Effective Flood Data

The State Digitized dataset was published as a part of the ‘Oregon Statewide Flood Hazard Database - FEMA Flood Insurance Studies – 2015’ available for download on the Oregon Spatial Data Library. When new flood maps have been digitized or adopted after 2015, the new data should be used instead of these datasets.

2015 State Digitized Flood Layer
The state digitized data were created by the Oregon Department of Land Conservation and Development (DLCD) in 2015. They are a digital representation of flood zones shown on FEMA paper maps with minor modifications added by DLCD in order to more accurately reflect recent topography and stream reaches. This data cannot be used for regulatory purposes.

2015 FEMA Q3 Flood Layer
The FEMA Q3 data is a digital version of existing FEMA FIRM (Flood Insurance Rate Map) maps. However, it is generally inaccurate because it was created on poor topography source data and needs revision because of the overall age of the data. The digital Q3 flood data are designed to provide guidance and a general proximity of the location of 100-year floodplain.

Data credits: Federal Emergency Management Administration (FEMA), Oregon Department of Geology and Mineral Industries (DOGAMI), and Oregon Department of Land Conservation and Development (DLCD), Oregon Geospatial Enterprise Office (GEO)

The Cascadia Subduction Zone (CSZ) is the tectonic plate boundary between the North American Plate and the Juan de Fuca Plate. These plates are converging at a rate of about 1.5 inches per year, but the movement is not smooth and continuous. Rather, the plates lock in place, and unreleased energy builds over time. At intervals, this accumulated energy is violently released in the form of a megathrust earthquake rupture, where the North American Plate suddenly slips westward over the Juan de Fuca Plate. This rupture causes a vertical displacement of water that creates a tsunami. Similar rupture processes and tsunamis have occurred elsewhere on the planet where subduction zones exist: for example, offshore Chile in 1960 and 2010, offshore Alaska in 1964, near Sumatra in 2004, and offshore Japan in March 2011.

A tsunami, often incorrectly referred to as a “tidal wave,” is a series of waves that can travel great distances from their source and inundate coastal areas. The time of arrival of tsunami waves depends on a location’s distance from the source event. For example, tsunami waves from local earthquakes may arrive between 5 and 30 minutes after the earthquake has started. Waves generated by distant sources may arrive hours after the earthquake has occurred. Tsunamis pose a real threat to Oregon coastal communities from Cascadia Subduction Zone earthquakes and also from distant earthquakes near Alaska or Asia. 

This viewer shows the estimated effects of a magnitude 9.0 Cascadia megathrust.  The estimated chance in the next 50 years of a great subduction zone earthquake of this size is between 7 and 12 percent, assuming that the recurrence is on the order of 530 ± 260 years and that the last one occurred about 312 years ago.

Statutory Tsunami Inundation Line
This line depicts the regulatory tsunami inundation boundary (Oregon Revised Statutes [ORS] 455.446 and 455.447) that was created by DOGAMI in 1995 to implement Senate Bill 379. It was created to prohibit the construction of new essential and special occupancy structures seaward of its location.

More information: OregonTsunami.org/Tsunami Regulatory Maps

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Cascadia Earthquake Expected Shaking
These data show the amount of shaking you can expect to feel if a magnitude 9.0 Cascadia Subduction Zone (CSZ) earthquake occurs. A CSZ earthquake will create a local tsunami that will inundate the Oregon coast.

More information: OregonTsunami.org

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Coastal erosion is a complex process involving many natural and human factors. It is a chronic hazard along many areas of the Oregon Coast, especially sand spits, bluffed coastline, and dune-backed beaches.

Chronic hazards are clearly evident along Oregon’s shores and include beach, dune, and bluff erosion; landslides, slumps, gradual weathering of sea cliffs; and flooding of low-lying coastal lands during major storms. The damage caused by chronic hazards is usually gradual and cumulative. The regional, oceanic, and climatic environments that result in intense winter storms determine the severity of chronic hazards along the coast. The coastal erosion hazard threatens property in its path and, in extreme events, can threaten human life as well.

These hazard zones represent areas of low to very high (active) erosion of beach or dune sediments by wave action, tidal currents, or drainage. Oregon residents who own structures on or near a beach or bluff should be aware of this hazard and its potential impact. NO DATA denotes coastal areas not mapped.

Coastal Erosion Data Limitations and Notes for zones along bluff-backed shorelines:

1. Erosion rates used to estimate widths of hazard zones are based on interpretation of relatively short historical series of aerial photography (1939 to present) and very limited lidar data acquired before 2008. Photos were georeferenced but not necessarily orthorectified and spatial locations may have considerable error.
2. Low hazard zones incorporate hypothetical landslide block failures assumed to fail in the event of a M9 Cascadia Subduction Zone earthquake. This may or may not happen.
3. The moderate hazard zone is simply defined by half the distance between the high and low hazard zones for bluff-backed shorelines.
4. Coastal erosion hazard zones have not been created for Lane, Douglas, and Coos Counties, and only partial data coverage exists for Curry County. 

For more detailed information, please see the following DOGAMI Publications used to create this hazard data layer: OFR O-01-03 (Tillamook County: Cascade Head to Cape Falcon); OFR O-01-04 (Clatsop County: Gearhart to Ft. Stevens); OFR O-04-09 (Lincoln County: Cascade Head to Seal Rock); OFR O-04-20 (Curry County: Sisters Rocks to North Gold Beach); OFR O-07-03 (Lincoln County: Seal Rock to Cape Perpetua); and OFR O-09-06 (Clatsop County: Seaside to Cape Falcon).

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Volcanic eruptions are most likely to occur in the Pacific Rim states, which include Oregon. The primary danger area around a volcano covers an approximately 20-mile radius, although there is some danger to people within 100 miles or more. Airborne ash from a volcano can affect people hundreds of miles away from the eruption. The most common volcano-related hazards are ash (tephra), lahars (volcanic mud flows), lava and debris flows, avalanches, and pyroclastic flows.

These data depict areas where volcanic hazards may occur during or after volcanic activity. Volcanoes can produce volcanic ash, mudflows, debris flows, avalanches of hot volcanic material, lava flows, and landslides. Residents and visitors to these areas should have an evacuation plan ready should volcanic activity begin.

DOGAMI used data from the U.S. Geological Survey (USGS) Cascades Volcano Observatory (CVO) for this web application. CVO maintains proximal and distal hazard zone data for five volcanic areas in the Western Cascades of Oregon. These areas include Mount Hood, Crater Lake, Newberry, Mount Jefferson, and the Three Sisters. HazVu shows these data as two hazard zones: the high hazard zone (proximal zone) and moderate hazard zone (distal zone). Any person or structure located within these hazard zones should have an evacuation plan ready should volcanic activity begin.

More information: USGS Cascades Volcano Observatory or DOGAMI/Mount Hood Risk Study

Data credit: U.S. Geological Survey Cascades Volcano Observatory (USGS CVO)

An earthquake is a sudden movement of a fault in the earth's crust, abruptly releasing strain that has accumulated over a long time. The movement along the fault produces waves of strong shaking that spread in all directions. If the earthquake occurs near populated areas, it may cause many deaths and injuries, and extensive property damage.

Oregon is affected by the Cascadia Subduction Zone where the Juan de Fuca plate slides underneath the North American plate. Earthquakes along this giant fault zone occur on average every 400-500 years, and can be extremely large. Oregon is also underlain by a large and complex system of faults that can produce damaging earthquakes. Although these smaller faults produce smaller earthquakes, they are often close to populated areas and damage can be great to structures nearby.

Earthquakes can trigger other geologic and soils failures that contribute to damage. While surface fault rupture can produce damage to facilities and infrastructure astride the fault, losses from this are minor compared to those resulting from strong ground shaking and associated ground failures. These include landslides, lateral spreading and slumping, and liquefaction (soft soil hazard).

Liquefaction (Soft Soil) Susceptibility

Deposits of loose sand or silt that are saturated with water commonly liquefy when shaken strongly or repeatedly by an earthquake. The liquefied materials lose most of their ability to support overlying soil layers and structures, and buildings and bridges sink and tilt, while riverbanks may slump and flow into the river channel. In many large earthquakes, much of the severe damage that occurs is due to liquefaction. Although liquefaction is very damaging, it only affects specific geologic deposits. DOGAMI created a data layer that generally represents where there are deposits that are susceptible to liquefaction if a strong earthquake were to occur. DOGAMI assigned liquefaction susceptibility values to the geologic units depicted in the Oregon Geologic Data Compilation (OGDC v5), and then categorized the values into Low, Moderate, and High susceptibility categories. Bedrock is not susceptible to liquefaction, so all areas that are mapped as bedrock in OGDC are not shown.

Expected Shaking

Soft or loose soil and near-surface geologic deposits can greatly amplify the shaking in an earthquake. Research sponsored by U.S. Geological Survey (USGS) and Federal Emergency Management Agency (FEMA) has defined a series of site classes that can be used to calculate the amount of amplification that will occur. These are called NEHRP (National Earthquake Hazard Reduction Program) site classes and range from A (very hard rock, no amplification) to F (very soft soil with special characteristics that require detailed investigation). The site classes are formally defined on the basis of the velocity of shear waves (one form of earthquake shaking) in the upper 30 m (100 ft) of the earth’s surface. Where shear wave velocity data are not available, general relationships between geologic material and site class have been established. DOGAMI used published and unpublished DOGAMI studies to create a statewide NEHRP site class data layer.

The USGS produces standardized seismic hazard maps for the nation through its National Seismic Hazard Mapping (NSHM) project. These take into account all possible earthquake sources and show the strength of shaking expected at several different probability levels including 10% chance in 50 years, 5% chance in 50 years, and 2% chance in 50 years. These maps show highly technical shaking parameters that are not readily understood by a non-technical audience and that do not relate simply to general earthquake damage. The maps also do not include the amplification effects of liquefaction in soft soils (as described above). DOGAMI created this derivative product that incorporates the site classes from the statewide NEHRP data and values representing perceived strength of shaking and general potential for damage.

Active Faults

Faults are considered active either when a large number of recorded earthquakes can be accurately located and shown to be along the fault, or where the fault has moved in geologically recent times and left a mark on the landscape or in young geologic deposits. These distinctions can be very difficult to make, and even more difficult to make accurately. The potentially active fault database created by DOGAMI for the state facility vulnerability assessment is a compilation of two primary fault databases; one from USGS, and the other from DOGAMI (OGDC v5).

Oregon’s digital geologic database (OGDC v5) contains tens of thousands of mapped faults, the vast majority of which have been inactive for millions of years. The USGS (through its NSHM project) has also compiled databases of potentially active faults for many states including Oregon. The USGS databases/maps are based on literature and include all faults for which there is some published evidence of movement (therefore earthquakes) in the past 10,000, 130,000, 750,000 or 1,600,000 years. However, the actual locations of the potentially active faults in this database were often taken from small scale compilation maps, and generally are not accurately drawn. Most of these faults are also contained in the OGDC database, but without detailed information regarding their potential activity. Therefore, to prepare the best available database of potentially active faults for Oregon, DOGAMI compared the faults in both databases and selected the version that reflected the most accurate location. In addition, the detailed information (attributes) from the USGS database was also carried forward and attached to each fault in the compilation regardless of its origin. The result is a fault database that combines the USGS information about fault activity with the most accurate available fault location. DOGAMI created buffers of the faults proportional to the accuracy and scale of the original source information. Therefore, faults with less accuracy and drawn at a smaller source scale (for example, scale 1:500,000) have a larger buffer than faults accurately located and drawn on a large scale (for example, scale 1:24,000).

Earthquake Data Limitations:

It is important to note that these data does not take into consideration structure type or construction materials to assess the ability of a building to withstand the earthquake hazard. All structures should have a site-specific study performed in order to more accurately assess its vulnerability to the hazard.

Active Faults
Potentially hazardous faults are those that have been identified by the U.S. Geological Survey as having moved in the last 1.6 million years (USGS Open-File Report 03-095). These faults may be the source of future damaging earthquakes, and severe ground disruption is possible within the buffer zones.

Fault lines were mapped largely from low-resolution geologic or topical maps, resulting in very poor location accuracy. DOGAMI reviewed the USGS database along with the Oregon Geologic Data Compilation (OGDC v5), which contains the best available digital geologic mapping for Oregon and is generally more detailed and accurate than the USGS sources. Where a positive correlation could be made, we substituted the more accurate fault line from OGDC for the original USGS line, while retaining the USGS data for each fault. Where a positive correlation could not be made, we retained the original USGS fault line.

Data credits: Oregon Department of Geology and Mineral Industries (DOGAMI) and U.S. Geological Survey (USGS)

Earthquake Epicenter (1971-2008)
An earthquake epicenter is the point on the Earth’s surface that is directly above the location where an earthquake originates.

More information: PNSN/Earthquake Map

Data credits: Pacific Northwest Seismic Network (PNSN) and Oregon Department of Geology and Mineral Industries (DOGAMI)

Earthquake Liquefaction (Soft Soil) Hazard
The intense shaking of an earthquake can cause soil liquefaction -- where loosely packed, water-logged sediments are transformed into a substance that acts like a liquid. Buildings and infrastructure sitting on these soft soils are likely to be severely damaged in an earthquake.

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Expected Earthquake Shaking
These data show the strongest shaking expected to occur during an earthquake in a 500-year period. The stronger the amount of shaking, the more structural damage will occur.

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Climate, geology, and topography combine to make portions of Oregon landslide-prone. Precipitation, earthquakes, and human activity are the main triggers of landslides.

This data shown provide a generalized (1:500,000 data scale; ~32 square ft grid) landslide susceptibility overview map of the entire state. The intended use of this overview map is to help identify regions (cities, counties, communities, portions of lifelines, watersheds, etc.) that may be at risk for future landslides. The map is designed to provide landslide hazard information for regional planning and specifically to identify areas where more detailed landslide mapping is needed.

More information: Open-File Report O-16-02, Landslide susceptibility overview map of Oregon

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

Landslide is a general term for deposits of soil or rock that have moved down slope. Slides generally occur on moderate to steep slopes, especially in weak soil and rock. Buildings constructed on landslides can be severely damaged when landslides reactivate.

Scarps are concave, steep areas of a slope where material has been removed due to landsliding. A head scarp is the area at the top of a slope where material has been removed due to landsliding.

Talus-colluvium is a general term for loose sediments built up at the base of a slope due to transportation by gravity.

Fans are accumulations of sediments that form at the mouths of steep canyons. Buildings on fans can be buried by sediment and debris during heavy rain storms.

Landslides are common, naturally occurring events in some parts of Oregon. Landslides occur when earth materials fall, slide, or flow down a slope or stream channel. They are classified by the type and rate of movement and the type of materials involved.

Landslides pose significant threat to many communities in Oregon and create challenges to development in steep terrain, coastal regions, and other landslide-prone areas. Landslides threaten transportation corridors, fuel and energy conduits, and community facilities. While not all landslides result in property damage, many landslides impact roads and other infrastructure, and can pose a serious life-safety hazard.

More information: Statewide Landslide Information layer for Oregon (SLIDO)

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)

State Owned/Leased Facility
Facilities owned or leased by the state of Oregon.

Data Limitations and Notes:

Data credit: Oregon Department of Administrative Services (DAS)

Public Buildings
The buildings shown represent schools and critical facilities that were evaluated in 2006 to assess their earthquake vulnerability. (Final results from this study were published by DOGAMI in 2007. See DOGAMI Open-File Report O-07-02.) This is not a comprehensive data layer of schools or critical facilities in the State. A handy list of buildings with RVS reports is also provided as Public Buildings with Seismic RVS Site Summary Reports.

Use the Public Buildings Search Tool on the map to access the vulnerability reports and click on the"RVS" button.

More information: DOGAMI/Statewide Seismic Needs Assessment Using Rapid Visual Screening (RVS)

Data credit: Oregon Department of Geology and Mineral Industries (DOGAMI)