The sun affects space weather, but does it cause earthquakes?

Many have wondered whether solar activity can be linked to earthquakes, but a recent study found no direct relationship between the two.

Scientists assembled historical records of the Sun’s interaction with Earth, looking at sunspots, solar wind, and magnetic storms. They then compared these with historical records of earthquake occurrence. They found no significant pattern between solar activity and more or larger earthquakes. There is no demonstrated way to use space data to predict future earthquakes.

The study was recently published in the journal Geophysical Research Letters. The research was conducted by Jeffrey Love with the USGS and Jeremy Thomas from Northwest Research Associates. The earthquake data were from the USGS, the sunspot data were from NOAA, the solar wind data were from NASA, and the geomagnetic data were from the British Geological Survey and Geoscience Australia.

The Author’s Perspective

“This research was conducted to advance our understanding of natural science and to test how the Sun affects Earth, ultimately helping protect the safety of our communities,” said USGS research geophysicist Jeffrey Love. “Even though we did not find a significant correlation between space measurements and earthquakes, we recognize that the Sun affects Earth in other ways. The USGS is dedicated to studying these natural phenomena, some of which are hazardous for a modern and technologically dependent society.”

“Of course it is always conceivable that some new and unexpected discovery will be made in the future, but it is also essential that we objectively evaluate the data and information that we have available now,” continued Love. “Just because one might think that a pattern exists does not mean that one actually exists. We need clear evidence to be convinced.”

Types of Solar and Space Activity

Everyone is familiar with weather systems on Earth like rain, wind, and snow. But space can also have a “weather” of sorts. The Sun’s behavior changes over time and this can cause the space environment surrounding Earth to change as well.

Magnetic storms, for example, are periods of time when Earth’s magnetic field is unusually active. How do they occur? The Sun is always emitting a wind of electrically charged particles, and when that happens abruptly, it can cause a magnetic storm.

Space weather can have important consequences for our lives on Earth’s surface. Large magnetic storms can cause the loss of radio communications, reduce the accuracy of GPS systems, damage satellite electronics and affect satellite opera­tions, increase pipeline corrosion, and induce voltage surges in electric power grids, causing blackouts. It is during magnetic storms that beautiful aurora borealis — or “northern lights” — are visible at high latitudes.

Now let’s talk about sunspots. A sunspot is a visibly dark region on the solar surface that corresponds to a concentration of solar magnetic energy and activity. If and when a large sunspot emerges on the face of the Sun, there is an increased chance for abrupt emission of strong solar wind velocity, and this can result in large magnetic storm at Earth. The number of sunspots waxes and wanes over the course of an 11-year solar cycle. The current cycle is unusually tame, but it could still change over the next few years.

Haitian woman carrying supplies amid the destruction from the January 2010 Haiti earthquake.

USGS Role 

The USGS Geomagnetism Program operates 14 observatories around the United States and its territories, which provide real-time ground-based measurements of the variable geomagnetic field. These measurements are used internally by the USGS, and they are used by partners in the United States National Space Weather Program, including NOAA, NASA, and the U.S. Air Force, to track the intensity of the magnetic storms generated by the Sun and its interaction with the Earth. The USGS Geomagnetism Program has also been working cooperatively with private industries that are affected by space weather and geomagnetic activity, including electric-power grid companies and the oil and gas drilling industry.

Can We Predict Earthquakes?

So far, the answer is no. Despite frequent claims to the contrary, no reliable short-term earthquake prediction method has ever been developed. Nor do scientists expect to develop a method in the foreseeable future.

However, based on scientific data, probabilities can be calculated for future earthquakes. For example, comprehensive assessments of long-term earthquake rates in California tell us there is roughly a 2-in-3 chance that a magnitude 6.7 or larger earthquake will strike in the next 30 years in the greater San Francisco Bay Area. Within the State of California as a whole, earthquakes this large are virtually certain (a 99 percent probability) in that same time frame.

Knowing the likelihood of future earthquakes allows prudent actions to be taken to mitigate their effects, no matter when they may happen to strike.

Listen to a podcast on earthquake prediction with Mike Blanpied, Associate Coordinator of the USGS Earthquake Hazards Program.

Climate Change and Solar Storms

Are solar storms related to climate change? Find out the answer by watching USGS Climate Connections.

Map of the May 15, 2013 earthquake in Virginia.

A magnitude 2.3 earthquake struck Louisa, Virginia, on May 15, 2013 at 7:01am local time.

Visit the USGS event page to learn more about this earthquake. If you felt this earthquake, report your experience on the “USGS Did You Feel It?” website.

Aftershock from 2011 Earthquake in Virginia

Wednesday’s earthquake was an aftershock from the magnitude 5.8 earthquake of August 23, 2011. That previous earthquake startled tens of millions of people in the eastern U.S. and southeastern Canada, and damaged schools and houses in the epicentral area.

Since the 2011 earthquake, more than 450 aftershocks have been recorded. These events were catalogued by the USGS National Earthquake Information Center (NEIC), using data from portable seismographs that were deployed by several organizations immediately after the earthquake.

More than 50 of these aftershocks were large enough to be felt, and 38 were the size of today’s earthquake, or larger. Scientists expect that these aftershocks will continue for many months.
Earthquakes in this area are not unprecedented, as they are within the Central Virginia seismic zone. This zone has been identified on USGS seismic hazard maps for decades as an area of elevated earthquake risk.

Although earthquakes are less frequent in the East, their damaging effects can extend over a much larger area as compared to the western United States. The difference between seismic shaking in the East versus the West is due in part to the geologic structure and rock properties that allow seismic waves to travel farther without weakening.

Looking Back to 2011

The earthquake from 2011 was among the largest to occur in this region in the last century. It is estimated that approximately one third of the U.S. population could have felt this earthquake, more than any other earthquake in U.S. history.

Around 148,000 people reported their ground-shaking experiences caused by the earthquake on the USGS “Did You Feel It?” website. Shaking reports came from southeastern Canada to Florida and westward to locations near the Mississippi River.

So what have scientists been up to since 2011? The USGS is engaged in many research projects to help ensure public safety in Virginia and other areas of the eastern U.S. Read a USGS feature story to learn more about the Virginia earthquake in 2011 and see the variety of related science efforts underway.

Start with Science

The USGS is actively studying earthquake hazards worldwide. The President’s requested FY14 budget includes a proposed increase in funding to improve earthquake monitoring in the eastern U.S. Expertise at the USGS includes earthquake monitoring and notification, earthquake impact and hazard assessments, geologic mapping and targeted research on earthquake causes and effects.

This image illustrates how earthquakes are felt over much larger areas in the eastern United States than those west of the Rocky Mountains. USGS “Did You Feel It?” data from the magnitude 5.8 earthquake on August 23, 2011 in central Virginia (green) and from one of similar magnitude and depth in California (red).

More Information

Read additional earthquake information for Virginia.

Read an article by USGS scientists in the American Geophysical Union newspaper EOS titled, “The 2011 Virginia earthquake: What are scientists learning?”

Multimedia

Watch video interviews with four people discussing their experiences near the epicenter of the Virginia earthquake in 2011.

Listen to two new podcast interviews with Associate Coordinator of the USGS Earthquake Hazards Program Mike Blanpied. The podcasts are:

• “A Year After the Virginia Earthquake: What More Do We Know?”
• “A Year After the Virginia Earthquake: Will the Shaking Continue?”

The USGS Red River of the North at Fargo streamgage in Fargo, N.D., takes automatic water level measurements every 15 minutes.

As residents of the Red River basin in North Dakota are faced with yet another major spring flood, water scientists and hydrologic technicians from the USGS are working in Fargo and throughout the river basin to collect important information on the volume of water that is flowing in the river. USGS field crews are taking streamflow and water level measurements on the Red River and its tributaries to document the current flood. The National Weather Service (NWS) uses the data collected by USGS hydrologists to inform its flood forecasts.

The Red River in downtown Fargo, N.D., began cresting, or reaching its peak water level, early Wednesday, May 1, at around 33.32 feet. As of late Wednesday morning, water level at the USGS Red River of the North at Fargo streamgage was 33 feet, which is three feet higher than the NWS major flood level designation. In Fargo, the river is expected to remain above the NWS major flood stage of 30 feet until Sunday. USGS hydrologists are monitoring the Fargo gage on a daily basis.

Previous major flood crests recorded by the USGS streamgage in downtown Fargo include: 38.81 feet, April 2011; 40.84 feet, March 2009; and 39.72 feet, April 1997.

The USGS has installed 12 rapid deployment streamgages at locations within the Red River of the North basin to collect water data where permanent streamgages have been damaged by the flood or do not exist. USGS crews will continue to follow the Red River flood north after the Fargo crest, with more staff moving to Grand Forks, Devils Lake, and Cavalier, N.D. Data for all of the USGS streamgages in the Red River of the North basin are available online.

USGS hydrologists return from measuring streamflow on the Red River in Fargo, N.D. The USGS Red River of the North at Fargo streamgage can be seen on the right in the image.

Flood First Responders

As soon as water starts to rise, specially trained USGS scientists and hydrologic technicians measure water levels, streamflows, and high water marks using state-of-the-art instrumentation. All of this information is crucial for NWS flood forecasts, for decisions by the U.S. Army Corps of Engineers (USACE) to operate spillways and levees, and for planning by Federal, state, and local emergency managers, first responders, and many other groups.

The widely distributed knowledge of stream conditions — knowledge based on direct, reliable, and timely data — is the means by which a modest investment in streamgages, combined with good science, can save money, help protect property, and even help save lives.

Measuring Streamflow

USGS field crews in North Dakota take streamflow measurements by boat each day during flooding using acoustic Doppler current profilers (ADCP). For the Red River measurements, the ADCP is attached to a large orange buoy, and dragged along the boat perpendicular to the water current to measure streamflow in cubic feet per second.  The ADCP also can be pulled across the stream from a bridge, when the flow is confined to the channel beneath the bridge.

On Tuesday afternoon, April 30, USGS crews measured a streamflow of 16,100 cubic feet per second near the USGS streamgage in downtown Fargo. USGS crews have made over 120 measurements of streamflow in the Red River basin in the last seven days in support of the USGS mission and to inform the flood forecast.

USGS Streamgages

The USGS operates a network of about 8,000 streamgages nationwide to help prepare for and respond to floods, and to enable the accuracy and confidence of NWS forecasting models.  Flood forecast and response, however, is only one of the many uses of streamgage information.

USGS hydrologist Dan Thomas shows media how the acoustic Doppler current profiler (on the right) measures streamflow on the Red River in Fargo.

A streamgage is a structure located beside a river or on a bridge that contains a device to measure and record the water level in that river. Generally, these measurements occur automatically every 15 minutes. For most streamgages, the data are sent via satellite back to a USGS office once every hour, and more frequently in times of flooding. There, critical information about gage height, or water level, and the flow of the river (measured in cubic feet per second) is made available to users in near real-time.

This USGS streamgaging network is in partnership with more than 850 Federal, state, tribal, and local agencies.

Due to recent budget cuts as a result of sequestration, the USGS will be obliged to discontinue operation of a substantial number of streamgages nationwide. Additional streamgages may be affected if partners reduce their funding to support USGS streamgages. It is possible that the funding mechanisms from Federal partners will also be affected, directly or indirectly, by sequestration reductions.

The USGS first sought to absorb budget cuts through curtailment of travel, training, hiring, and other expenditures not deemed mission-critical. Even though the operation of most streamgage equipment is highly automated, the data produced need field verification, which requires trained technicians to visit the streamgages on a regular basis. During flood events, the need for frequent visits becomes even more critical as the data is used by first responders to support the protection of life, property, and the environment.

Where Can You Find USGS Flood Information?

The USGS is constantly refining, innovating, and updating its ability to deliver river information to emergency managers, first responders, other Federal agencies, and you and your family before, during, and after a flood.

If you want to see areas where river levels are higher than normal right now, you can go to the USGS WaterWatch site and view a map of the thousands of real-time streamgages that constantly monitor the Nation’s rivers and streams. For example, you can access a map of the flood and high streamflow locations in North Dakota through the WaterWatch site.

To put that number in context, the USGS and the NWS are working together to create visual products, called flood inundation map libraries, that show you estimates of where the water will be and what roads, yards, and buildings will be affected when a river or stream reaches a certain stage.

You can also receive automatic notifications from streamgages near you sent directly to you as an email or text message when water levels exceed certain thresholds. Sign up for this USGS WaterAlert service by selecting a state, checking the “Surface Water” box, and clicking on your streamgage of choice.

Links:

USGS North Dakota Water Science Center: http://nd.water.usgs.gov/

When Floods Hit, the USGS is There: http://www.usgs.gov/blogs/features/usgs_top_story/when-floods-hit-the-usgs-is-there/?from=title

Main USGS Flood Site: http://water.usgs.gov/floods

Real-time USGS Water Data: http://waterdata.usgs.gov/nwis/rt

USGS Red River of the North at Fargo Streamgage: http://waterdata.usgs.gov/nd/nwis/uv?site_no=05054000&format=gif&period=31

Flood Inundation Interactive Mapper: http://wim.usgs.gov/FIMI/FloodInundationMapper.html

Additional information about Flood Inundation Mapping: http://water.usgs.gov/osw/flood_inundation/

WaterAlert: http://water.usgs.gov/wateralert/

USGS scientists use an acoustic Doppler current profiler (ADCP) to measure streamflow and water currents at Ditch 14 near Fargo, N.D., in 2011.

As flooding continues in parts of Missouri, Iowa, Illinois, Wisconsin, Michigan, and Indiana due to heavy rainfall over the past seven days, the U.S. Geological Survey is maintaining its response efforts and preparing for continued flooding in the Northern Plains and upper Midwest.

So far this spring, USGS streamgages have measured approximately 17 peaks of record, and numerous flood peaks that have been the largest in more than 50 years. The USGS will be in flood response mode for the next several days as flooding continues down the Wabash and White Rivers in Indiana, the Illinois River in Illinois, and along the middle Mississippi River.

The USGS is also ready to deploy field crews to the Red River of the North Basin in North Dakota and Minnesota as air temperatures rise above freezing and snowmelt begins, and has installed seven rapid deployment gages at locations in the basin where streamflow data is needed but otherwise unavailable. Runoff and subsequent flooding is expected to begin this weekend, especially in Fargo, N.D., and Oslo, Minn.

Preparation Helps Save Lives and Property

As soon as water starts to rise, specially trained USGS scientists and hydrologic technicians measure water levels, streamflows, and high water marks using state-of-the-art instrumentation. All of this information is crucial for National Weather Service (NWS) flood forecasts, for decisions by the U.S. Army Corps of Engineers (USACE) to operate spillways and levees, and for the planning of Federal, state, and local emergency managers, first responders, and many other groups.

This reliable, timely, and widely distributed understanding of stream conditions is the means by which a modest investment in streamgages, combined with good science, can save money, help protect property, and even help save lives.

USGS Streamgages

The USGS operates a network of about 8,000 streamgages nationwide to help prepare for and respond to floods, and to enable the accuracy and confidence of NWS forecasting models.

A streamgage is a structure located beside a river that contains a device to measure and record the water level in that river. Generally, these measurements occur automatically every 15 minutes. For most streamgages, the data are sent via satellite back to a USGS office once every hour, and more frequently in times of flooding. There, critical information about gage height, or water level, and the flow of the river (measured in cubic feet per second) is made available to users in near real-time.

USGS crews install a rapid deployment streamgage on the Boise River near Parma, Idaho, in 2012.

This USGS streamgaging network is in partnership with more than 850 Federal, state, tribal, and local agencies.

Due to recent budget cuts as a result of sequestration, the USGS will be obliged to discontinue operation of up to 375 streamgages nationwide. Additional streamgages may be affected if partners reduce their funding to support USGS streamgages. It is possible that the funding mechanisms from Federal partners will also be affected, directly or indirectly, by sequestration reductions.

The USGS first sought to absorb budget cuts through curtailment of travel, training, hiring, and other expenditures not deemed mission-critical. Even though the operation of most streamgages is highly automated, the gages still require periodic instrument calibration, communication adjustments, battery replacement, and site maintenance (especially after high water events) to ensure accurate readings and physical stability.

Recent USGS Flood Work in Your State

If your state is experiencing flooding, USGS crews are out on the job. What’s been happening in the most severely flooded states over the past week?

Illinois

At least 10 USGS streamgages in Illinois with more than 20 years of record have measured the highest flood levels ever recorded. More record levels are expected as flooding moves downstream. USGS crews are expected to track the movement of the floodwaters down the Illinois River, the Rock River, and major tributaries over the next few days.  Many of the Illinois River floodwaters are expected to exceed records and may result in major flooding that overtops levees.

The USGS Illinois Water Science Center is working with the NWS and USACE to acquire the streamflow information they need for prediction and flood control efforts. As of Monday, 53 USGS streamgages in Illinois were at or above flood levels as a result of the precipitation that began on Tuesday, April 16.

Indiana

At least three USGS streamgages in north-central Indiana have measured the highest water levels in more than 20 years of recorded data, and 32 streamgages are above flood stage. USGS crews in Indiana are continuing to make streamflow measurements along the middle and lower Wabash River and the lower White River. There have been at least two deaths attributed to flooding around the state. According to the Indianapolis Star, more than 100 homes were evacuated in the Kokomo and Elwood areas due to high water.

Moderate flooding is expected to continue over the next several days. Four USGS crews will measure streamflow at ten locations following the flood peak as it progresses down the Wabash and the White Rivers. Three crews are also out setting high-water marks to document the extent of the flooding that occurred on Friday and this past weekend.

USGS streamgages like this Red River of the North at Fargo gage in downtown Fargo, N.D., provide real-time water level and streamflow data during floods.

The USGS Indiana Water Science Center has been working with the Indiana Department of Natural Resources and NWS Ohio River Forecast Center to coordinate ongoing flood response efforts.

Iowa

Flooding occurred in eastern and south-central Iowa due to heavy rainfall in areas of saturated soil, with about 23 streamgages above the NWS flood stage and approximately six gages above NWS major flooding levels. Johnson County issued a disaster declaration due to flash flooding, and temporary flood protection has been deployed by the City of Cedar Rapids along Indian Creek. The eastern half of Iowa experienced moderate flooding in a line from Dubuque to Chariton, and many roads in the Iowa City area have been closed.

Multiple USGS Iowa Water Science Center crews continue to take discharge measurements and are measuring streamflow over several flooded roadways.

Michigan

The Lower Peninsula of Michigan has experienced some flooding since heavy rainfalls began on Tuesday, April 9. Most flooding in the first few days was confined to smaller streams and the Cass, Tittabawassee, and Saginaw Rivers. Heavy rains began again on Wednesday, April 17, and continued sporadically through Friday, April 19. Flood impacts in Ionia County, located northwest of Lansing, were especially severe, with some bridges over small streams washed out and a large area near the city center under water.

On April 19, the NWS reported that 22 USGS streamgaging stations in the state had reached flood stage, 13 streamgages were approaching flood stage, 17 gages had reached the minor flooding category, and seven gages recorded moderate flooding. By Saturday, April 20, several gages in the western part of the Grand River Basin were reporting stages in the major flood category, with Comstock Park, upstream of Grand Rapids, particularly affected.

USGS Michigan Water Science Center technicians from the Lansing and Grayling field offices have been working closely with the NWS offices in Grand Rapids and White Lake, and the North Central River Forecast Center in Chanhassen, Minn., making measurements at many locations at or near peak stage in the Grand, Kalamazoo, Muskegon, and Saginaw River Basins.

Missouri

In Missouri, moderate to major flooding is occurring on the upper and middle Mississippi River. A USGS Missouri Water Science Center crew is supporting the USACE St. Louis District in monitoring water levels at various lock and dam locations.

Where Can You Find USGS Flood Information?

The USGS is constantly refining, innovating, and updating its ability to deliver river information to emergency managers, first responders, other Federal agencies, and you and your family before, during, and after a flood.

WaterWatch

If you want to see areas where river levels are higher than normal right now, you can go to the USGS WaterWatch site and view a map of the thousands of real-time streamgages that constantly monitor the Nation’s rivers and streams. But how do you put that number in context?

The USGS and the NWS are working together to create visual products, called flood inundation map libraries, that show you estimates of where the water will be and what roads, yards, and buildings will be affected when a river or stream reaches a certain stage.

WaterAlert

You can get automatic notifications from streamgages near you sent directly to you as an email or text message when water levels exceed certain thresholds. Sign up for this USGS WaterAlert service by selecting a state, checking the “Surface Water” box, and clicking on your streamgage of choice.

Links:

Flood Inundation Interactive Mapper: http://wim.usgs.gov/FIMI/FloodInundationMapper.html

Additional information about Flood Inundation Mapping: http://water.usgs.gov/osw/flood_inundation/

WaterAlert: http://water.usgs.gov/wateralert/

Main USGS Flood Site: http://water.usgs.gov/floods

Real-time USGS Water Data: http://waterdata.usgs.gov/nwis/rt

Map of the April 16, 2013 earthquake east of Khash, Iran.

A magnitude 7.8 earthquake struck east of Khash, Iran, on April 16, 2013 at 10:44:20 UTC.

Visit the USGS event page on this earthquake.

For an estimate of the earthquake’s impact, visit the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) website.

Read additional earthquake information for Iran.

If you felt this earthquake, report your experience on the “USGS Did You Feel It?” website for this event.

Learn more about the USGS Earthquake Hazards Program.

Map of the April 9, 2013 earthquake southeast of Bandar Bushehr, Iran.

A magnitude 6.3 earthquake struck southeast of Bandar Bushehr, Iran, on April 9, 2013 at 11:52:50 UTC.

Visit the USGS event page on this earthquake.

For an estimate of the earthquake’s impact, visit the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) website.

Read additional earthquake information for Iran.

If you felt this earthquake, report your experience on the “USGS Did You Feel It?” website for this event.

Learn more about the USGS Earthquake Hazards Program.

A devastating sinkhole occurred in Florida on February 28, 2013, raising questions and concerns about this incredible phenomenon. Around 20% of the U.S. lies in areas susceptible to sinkhole events, highlighting the need for research and to be informed about this hazard.

What is a Sinkhole?

Geologically, a sinkhole is a depression in the ground that has no natural external surface drainage. Basically this means that when it rains, all of the water stays inside the sinkhole and typically drains into the subsurface.

Sinkholes are most common in what geologists call, “karst terrain.” What’s that? These are regions where the type of rock below the land surface can naturally be dissolved by groundwater circulating through them. Soluble rocks include salt beds and domes, gypsum, and limestone and other carbonate rock. Florida, for instance, is an area largely underlain by limestone and is highly susceptible to sinkholes.

When water from rainfall moves down through the soil, these types of rock begin to dissolve and spaces and caverns develop underground. Sinkholes are dramatic because the land usually stays intact for a period of time until the underground spaces just get too big. If there is not enough support for the land above the spaces, then a sudden collapse of the land surface can occur.

USGS map showing areas of the contiguous United States that are underlain by relatively soluble rocks with potential for cave and natural sinkhole formation. Note that the delineated areas are generalized; actual potential for sinkhole development varies locally within each region.

Keep in mind though that while collapses are more frequent after intense rainstorms, there is some evidence that droughts play a role as well. Areas where water levels have lowered suddenly are more prone to collapse formation.

Areas Most Susceptible

About 20% of our country is underlain by “karst terrain” and is susceptible to a sinkhole event. The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.

Different Types and Various Severities

Collapse sinkhole in a salt dome in Daisetta, Texas (September 2008). Photo Credit: Randall Orndorff, USGS

Sinkholes can be characterized into two types. First, there are cover-collapse sinkholes, which can develop abruptly (over a period of hours) and cause catastrophic damages. Secondly, there are cover-subsidence sinkholes, which form slowly over time with the ground gradually subsiding or deflating. These types of events can be less noticeable and go undetected for long periods.

Sinkhole collapses can range in size and severity. Sinkholes can vary from a few feet to hundreds of acres and from less than one to more than 100 feet deep. Sinkholes can have dramatic effects, especially in urban settings. They can contaminate water resources and have been seen to swallow up swimming pools, parts of roadways, and even buildings.

Is There a Sinkhole on Your Property?

This is a difficult question, and unfortunately there isn’t a very efficient system to determine this quite yet. It is recommended that people constantly observe their property for things such as small holes in the ground or cracks formed in a structure’s foundation. People can also check to see if they live in areas underlain by soluble rock, and they can do so by checking with county offices, local or state geological surveys, or the USGS.

Even Humans Cause Sinkholes

While sinkhole collapses are frequent in karst areas, there are a variety of other circumstances that can lead to such events. Many sinkholes form from human activity. Collapses can occur above old mines, from leaky faucets, when sewers give way, or due to groundwater pumping and construction.

Think about all the changes that occur when water-drainage patterns are altered and new systems are developed. And when industrial and runoff-storage ponds are created, the resulting substantial weight of the new material can trigger an underground collapse of supporting material.

Aquifer systems are another factor in sinkholes. The sediment above the aquifer system may be delicately balanced by ground-water fluid pressure, meaning that the water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes. If pumping results in a lowering of groundwater levels, then underground structures could fail and thus sinkholes can occur.

Cover-collapse sinkhole in limestone near Frederick, Maryland (September 2003). Photo Credit: Randall Orndorff, USGS

Start with USGS Science

Starting with science is important to understanding where sinkholes are likely to occur and making the best decisions to protect life and property. Scientists at the U.S. Geological Survey (USGS) play a key role by developing geologic maps of the nation.

By mapping the nation, the USGS contributes important geologic and topographic information needed to understand karst regions and local areas. Detailed geologic mapping helps to define areas of soluble rock at the surface and in the subsurface, thus educating the land planners, policy makers, and the public about sinkhole risk.

These USGS maps and data are essential to many other purposes, including assessing ground-water quality and contamination risks; predicting earthquake, volcano, and landslide hazards; characterizing energy and mineral resources and their extraction costs; waste repository siting; land management and land-use planning; and general education.

Learn More

Learn more about sinkholes by reading an online overview story or a USGS fact sheet.

To see a catalog of all geologic maps for the country, visit the USGS National Cooperative Geologic Mapping Program website. On that site, you can browse through the National Geologic Map database, which includes maps published by the USGS and state geological surveys.

Shakemap of the March 11, 2013 earthquake in southern California.

A magnitude 4.7 earthquake struck in southern California on March 11, 2013 at 16:56:06 UTC. The earthquake was approximately 12 miles ESE of the town of Anza.

Visit the USGS event page on this earthquake.

For an estimate of the earthquake’s impact, visit the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) website.

For information about tsunami watches, warning or advisories, visit the National Oceanic and Atmospheric Administration (NOAA) tsunami website.

Read additional earthquake information for California.

If you felt this earthquake, report your experience on the “USGS Did You Feel It?” website for this event.

Learn more about the USGS Earthquake Hazards Program.

Time: Thursday, February 28, 2012 • 7-8pm

Speaker: Nathan Wood

Location: 345 Middlefield Road, Building 3 Auditorium, second floor, Menlo Park, CA 94025

Phone:  650-329-4000

FREE and Open to the Public

Follow this event live streaming over the Internet!

This announcement and directions can be found online.

Landslides associated with the March 27, 1964 Alaska earthquake caused $960 million in damage (expressed in 2011 dollars). This landslide in Anchorage’s Turnagain Heights neighborhood, along a steep bluff fronting Knik Arm on Cook Inlet, was about 1.5 miles long and up to 1/2 mile wide, and destroyed many of the city’s finest homes.
Photo by USGS

As a rainy winter plods on, scientists, resource managers and property owners from coast to coast cast worried eyes on America’s hillsides for signs of this common natural geologic hazard – a landslide.

Landslides can happen anyplacethat has unstable hillslopes and a contributing factor such as an earthquake, a wildfire severe enough to alter soil properties, human modification of the landscape or, most commonly, rain. The West Coast, particularly California, is vulnerable to landslides because of its steeplands, its seasonal rainfall patterns, and the way its ongoing tectonic deformation exposes vulnerable sediments,not to mention the large population that lives in areas that could be affected by landslides, said  Lynn Highland, a geographer with the USGS National Landslide Information Center in Golden, Colo.

The USGS is working on several fronts to better understand landslide hazards both in the United States and internationally and to provide information that will help resource managers and the public make safe choices in the face of landslide hazards. USGS scientists have mapped landslides, studied why landslides can repeat in the same places, created near-real-time monitoring systems, and calculated the economic costs of landslides. A “Did You See It” feature recently added to the USGS Landslide Hazards Program’s website allows people to report landslides anywhere in the United States and to see where landslides have been reported in the past.

An oblique LIDAR image of La Conchita, Calif., reveals the community’s grim landslide history. The 1995 landslide is outlined in blue and the 2005 landslide in yellow, while a red line overhead outlines the main scarp of an ancient landslide that involved the entire bluff. Arrows show other landslides in the area. The deep canyon on the left produced major debris flows in both 1995 and 2005.
Image by Todd Stennett, Airborne 1 Corp., El Segundo, Calif.

In California, most people think of landslides as following prolonged heavy rain. They reference such tragedies as the San Francisco Bay Area’s Love Creek landslide, which claimed 10 lives in January 1982, or the Scenic Drive landslide in nearby La Honda, which rendered uninhabitable more than $40 million worth of homes in February 1998. Intense West Coast storms that hit from mid-December to April are much more likely to trigger landslides than storms earlier in the season, because they add water to steepland soil that has already accumulated significant moisture in its fissures and pores, said USGS research geomorphologist Jonathan Stock.  In late November 2012, a heavy storm brought more intensive rain to some parts of the Bay Area than they received during the 1982 disaster. “But there was no widespread landsliding, because the soil pores were not yet fully saturated,” Stock said.

Stock and USGS research civil engineer Brian Collins have created a near-real-time landslide monitoring system in the San Francisco Bay Area. Sensors at four stations monitor pore water pressure and soil moisture conditions that could precede widespread landsliding.  Similar USGS monitoring systems exist in parts of Oregon, southern California and Colorado. Years of observation using such systems are typically required to understand what combinations of soil moisture and precipitation lead to landslides.

It’s already known that many California landslides are associated with the airborne masses of water vapor called atmospheric rivers, which, because they originate in the semitropics of the Pacific Ocean and travel west, can be tracked several days before they reach the West Coast. Now, Stock, Collins and others are working on ways to integrate precipitation and soil moisture data to forecast susceptibility to widespread landsliding.

Hillsides that have been swept by wildfires also pose risk of post-fire debris flows. These post-fire debris flow warnings are issued by the National Weather Service to local emergency managers and the public. Here, the triggering process is different. Not only is vegetation destroyed that might intercept rainfall, but soil particles themselves can become coated with volatilized organic matter that makes them water-repellent, explained USGS emeritus research geologist Sue Cannon. More rainwater cascades off hillslopes than soaks in.

As it moves downslope, the rainwater collects increasing amounts of soil and rocks. The mix becomes denser and heavier as it travels, and in as little as 15 minutes can become a debris flow powerful enough to threaten structures or block highways, as happened after the 2009 Station fire in southern California and the June 2012 High Park fire west of Fort Collins, Colo.

Because this process does not depend on soil saturation, post-fire debris flows can be triggered by the first big rain of the year, Cannon said. USGS scientists created debris-flow hazard maps of the High Park burn area and found that some drainage basins had up to an 84 percent chance of producing debris flows if they received 25mm (just under an inch) of rain in an hour. USGS has also installed monitoring sensors in areas with high potential for post-fire debris flows, including basins burned by the 2009 Station Fire that threatened several cities at the base of the San Gabriel Mountains in southern California.  The potential for post-fire debris flows generally lessens after two to three years, however, as burned areas become revegetated and sediment supplies are depleted.

This slide on San Pedro, Calif.,’s Paseo del Mar began moving over a period of weeks in November 2011. On Sunday, Nov. 20, the landslide moved abruptly, causing the roadway to collapse.
Photo by Los Angeles County Supervisor Don Knabe

USGS’ Landslide Hazards Program has developed methods to characterize debris-flow hazards from recently burned areas, including empirical models to predict for a given point along a drainage network 1) the volume of debris flow; 2) the probability of debris flow; and 3) the downstream path that the debris flow would take . “A set of models were originally developed for burned areas in the Intermountain West,” Cannon said, “and we are now in the process of developing models specific to conditions within Southern California because of differences in the region’s fire behavior and the large number of people potentially impacted there.”

An important part of mitigating landslide hazards is the understanding that landslides can recur at the same sites, Stock said. Water can seep off the toe of an old slide and cause failures there, he said. Other slope failures calve off earlier failures, as happened in the seaside community of La Conchita, Calif., in 1995 and again in January 2005. No one was injured in the 1995 event, but a debris flow a decade later killed 10 people. Both landslides were within the footprint of an ancient landslide on the slope behind them, as aerial photography and LIDAR imagery reveal. La Honda’s Scenic Drive homes sat atop an ancient landslide as well.

Landslide hazard maps of many areas are available from USGS as well as the California Geological Survey and other states’ geological offices, along with resources and tips on how to help avoid landslide hazards. These landslide maps identify areas where the greatest threat to property exists from the movement of deep-seated landslides.

Other USGS science investigates how landslides fit into larger ecological processes and economic assessments. Highland studies direct economic losses from landslides in addition to indirect losses.  Landslide losses in many cases are ascribed to earthquakes or floods, but actually are due to landslides that the earthquakes or floods have triggered. In the case of the 1964 Alaska earthquake, much of the economic damage was actually done by landslides, Highland said. Other USGS scientists are studying large-scale landslide hazards threatening people and property in coastal Oregon and Washington, Appalachia, China, Micronesia, and Haiti, as well as rockfall associated with the 2001 earthquake in Nisqually, Wash., and the 2011 earthquake in Mineral, Va.

More USGS landslide resources:

The Landslide Handbook: A Guide to Understanding Landslides

FAQs on landslides

Other USGS publications on landslides

Images of landslides around the world

Pilot project toward a national landslide inventory

USGS geologists working on landslide research

How to find landslide information in your state

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