National Preparedness Month 2020: Earthquakes and Tsunamis

USGS:  Start with Science

The USGS works with many partners to monitor, assess and conduct research on a wide range of natural hazards. USGS science provides policymakers, emergency managers and the public the understanding needed to enhance family and community preparedness, response and resilience.

By identifying potential hazard scenarios and using USGS hazards science, federal, state, and local agencies can mitigate risk. For example, USGS science can be combined with population data to inform evacuation routes; with local building and land-use codes to reduce impacts to critical facilities; and with emergency preparedness plans to ensure appropriate steps are taken before, during, and after an event. In addition, USGS science can inform planning for major infrastructure investments – such as dams and reservoirs – and to strengthen private-property standards and materials, which help make homes and communities more resilient to natural hazards. The annual National Preparedness Month is a perfect time to consider how you can keep your family safe from all types of natural hazards.

Earthquakes

Earthquake hazards are a national concern, with nearly half of Americans living in areas prone to potentially damaging earthquakes. The USGS provides information and tools to reduce earthquake losses across the Nation. These include hazard assessments, earthquake scenarios such as the annual ShakeOut events and the HayWired scenario, comprehensive real-time earthquake monitoring and public-preparedness handbooks.

Collection of USGS still images taken after the January 17, 1994 Northridge earthquake highlighting the damage to buildings and infrastructure.

(Credit: No name provided, USGS. Public domain.)

Now, imagine if fire stations could be warned to open the firehouse doors before damaging seismic waves of an earthquake arrive and jam them shut; just a few moments of advance notice can make all the difference. Likewise, if trains could be slowed or stopped; if water and other utilities could be shut down; and if people could have additional time to “drop, cover and hold on,” saving lives.

The USGS and its partners are making that a reality by building an Earthquake Early Warning System for the West Coast of the United States called “ShakeAlert,” which began providing public alerts in California in fall 2019, and has already distributed alerts for eight potentially damaging (magnitude 5 and above) earthquakes over the past year via the Wireless Emergency Alert System.

Earthquake Activity in 2020

Parts of the United States have experienced some significant earthquake activity in 2020.  In January 2020, a magnitude 6.4 (M6.4) earthquake in Southwest Puerto Rico occurred as part of a sequence of events that included more than a dozen magnitude 5 and above earthquakes, and more than 1,500 magnitude 3 and above events, potentially large enough to be felt locally.

The U.S. Geological Survey has released a report on the potential duration of aftershocks of the 2020 Southwest Puerto Rico earthquake sequence (series) to guide public policy decisions, other actions, and help people stay safe and care for themselves and each other.

i) AFTERSHOCK FORECAST*
Aftershocks are normal and some will be larger than others, but there will be fewer over time.

M3+
earthquakes will occur daily for months, and then weekly for years.

YEARLY CHANCE OF M5+currently >99% and will stay over 50% for 3 – 10 years

YEARLY CHANCE OF M6+currently 50% and will stay over 25% for 3 months – 3 years

YEARLY CHANCE OF M7+currently 8% and will stay over 5% for 1 – 10 months

YEARLY CHANCE OF M7+will stay over 1% for 2 – 10 years

The yearly chance is the likelihood of an earthquake happening any time within a year-long period. Future aftershocks will be located in the same area as past events. These aftershocks do not change the risk on other parts of Puerto Rico.

* The results in this report are based on the current behavior (as of January 17, 2020) of this aftershock sequence and may need to be modified if that behavior changes, including if a larger earthquake occurs. 

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Although earthquakes are normal in Puerto Rico they can be unsettling. Feeling anxious or stressed? 

1-800-981-0023
La Línea PAS (Primera Ayuda Sicosocial) Crisis Counselors

A special thanks to our Advanced National Seismic System (ANSS) partner, the Puerto Rico Seismic Network (PRSN) at University of Puerto Rico at Mayaguez. Background: Building destruction in Puerto Rico, January 2020. 

i) Forecast Report at www.usgs.gov/pr-forecast-2020

USGS Identifier
Science for a Changing World

Federal Emergency Management Agency (FEMA)

U.S. Department of the Interior
U.S. Geological Survey

(Public domain.)

USGS earthquake scientists worked closely with its Advanced National Seismic System partners at the Puerto Rico Seismic Network to deploy instruments to better monitor the aftershock sequence. Together, they generated an aftershock forecast to provide information on the evolving likelihood of both aftershocks and larger events, and published an aftershock duration report to support FEMA in their emergency-management response to the earthquake sequence.

The Puerto Rico earthquake appeared to involve multiple faults both onshore and offshore that form a complex pattern. The earthquake sequence caused damage to numerous structures in southern Puerto Rico, including destruction of several buildings and damage to the main powerplant that resulted in intermittent power outages across parts of the island. USGS geologists examined ground failure (landslides, liquefaction, and cracking) near the epicenter of the earthquake to calibrate the reliability of a USGS ground-failure science.

Since March 2020, there have been a number of significant earthquakes across the Intermountain West region of the United States. The USGS has worked closely with state and local partners to understand and document these earthquakes, despite the ongoing COVID-19 pandemic. USGS activities include providing seismic instrumentation, tasking of satellites and analyzing satellite imagery, and deploying scientists to collect ephemeral field and seismic data. A summary of the events is provided below: 

The 18 March 2020 M5.7 Magna, UT earthquake occurred north of Magna, Utah (just west of Salt Lake City) as the result of normal faulting in the shallow crust of the North America plate. This was the most significant earthquake in Utah in 86 years. The USGS provided seismic instrumentation to the University of Utah Seismic Stations. 
The 31 March 2020 M6.5 Stanley, ID earthquake occurred near the northern end of the Sawtooth Mountains, Idaho. This is the largest earthquake in Idaho since the 1983 Borah Peak earthquake. The USGS provided technical expertise to the Idaho Geological Survey and sent temporary seismic stations that were installed by Boise State University. USGS scientists deployed to the region in September 2020 to evaluate surface effects resulting from the earthquake. 
The 15 May 2020 M6.5 Monte Cristo Range earthquake occurred northwest of Tonopah, Nevada. This was the largest earthquake in Nevada since the 1954 Dixie Valley and Fairview Peak events. The USGS deployed two teams of scientists. One team set up seismic instruments to image the causative fault. The second team documented minor surface rupture and ground cracks that resulted from the earthquake. 
The 24 June 2020 M5.7 Lone Pine earthquake occurred southeast of Lone Pine, California. This significant earthquake occurred less than one year after the 2019 Ridgecrest earthquake sequence. The M5.7 Lone Pine earthquake caused significant rockfall in the Sierras, which impacted the Whitney Portal trail head and campground. USGS scientists deployed to the region to document ground failure features. 
On August 9, 2020, a M5.1 earthquake struck near the town of Sparta, North Carolina at just after 8 o’clock in the morning. The earthquake caused minor damage to buildings and infrastructure such as roads and water lines. Earthquakes of this size are rare in North Carolina, with this being the largest in the state since a similar-sized earthquake near Asheville in 1916. Personnel from the University of Memphis, who operate a seismic network in the region as part of the USGS Advanced National Seismic System, installed four additional seismometers in the area to better monitor aftershocks from the earthquake. So far, researchers have identified as many as 8 small foreshocks and 184 aftershocks. 

Tsunamis

Tsunami events in the United States are relatively rare compared to the rest of the world, but that does not mean the potential risk is low or should be ignored. Many U.S. coastal communities are threatened by tsunamis, and recent disasters elsewhere in the world have demonstrated how destructive these waves can be. Tsunami waves can arrive within minutes when created by a local source or within hours when created by distant earthquakes across ocean basins.

The USGS tsunami and tsunami hazards research supports local and state emergency managers in their efforts to prepare communities and reduce the potential impacts of future tsunamis by studying how and where tsunamis could form, the frequency and size of past tsunamis, and how coastal communities may be vulnerable to tsunami hazards. The USGS studies recent, historic, and prehistoric tsunamis to better understand impacts, processes, and causes. Field investigations focusing on sediment left by tsunamis document where and when tsunamis have impacted U.S. coastlines in the past. The USGS also studies how earthquakes, landslides and volcanic eruptions generate tsunamis to understand all potential causes and to identify tsunami hazard zones.

Tsunami waves, view to the northwest

This animation shows the evolution of tsunami waves caused by the December 26, 2004 Sumatra-Andaman earthquake. Because it takes approximately 8 minutes for the entire fault to break, tsunami waves generated near the epicenter have propagated part way into the Bay of Bengal by the time the earthquake has just started to generate more tsunami waves near the Andaman Islands. These waves then cross the Andaman Sea toward Thailand.

(Public domain.)

The USGS also studies how coastal communities are vulnerable to tsunami hazards by evaluating the number and type of people or businesses in tsunami hazard zones, as well as likely evacuation times for each of these coastal communities. USGS vulnerability studies support local, state, and regional efforts to minimize loss of life from local tsunamis by understanding how communities are threatened, estimating what type of intervention could be most effective in saving lives, identifying where new evacuation structures (e.g., a building, a town, etc.) may be most needed, improving communications about local evacuation routes, and understanding future vulnerability to tsunamis.

USGS vulnerability studies also support distant tsunami evacuation planning by identifying ways to minimize potential traffic issues and characterizing the trade-offs of various evacuation policies. The USGS has developed free software to help coastal planners do their own pedestrian evacuation modeling for tsunami threats. All of these studies and tools provide officials with the ability to develop outreach, preparedness, and evacuation plans that are tailored to local conditions and address both local and distant tsunami threats.

As part of an international tsunami survey team, Andy Moore of Kent State University takes measurement of a snapped-off tree trunk in Leupueng, Aceh in 2005, shortly after the deadly tsunami struck the island of Sumatra.

(Credit: Guy Gelfenbaum, USGS Pacific Coastal and Marine Science Center. Public domain.)

Additional Information

Latest Earthquakes Worldwide

Sign Up for Earthquake Notifications

The Great ShakeOut 2020

U.S. Tsunami Warning Service

Source: Alerts2