Tag Archives: USGS

MyShake: New App Unveiled for California Earthquake Early Warning

As my colleague Mohsen Rahnama reminded us in his recent blog, the last destructive earthquake to strike Northern California was on October 17, 1989. Loma Prieta was a magnitude 6.9 earthquake which resulted in 63 deaths and about four thousand injuries. The epicenter was about ten miles northeast of Santa Cruz, and seismic waves took about 30 seconds to reach San Francisco. But there was no way of communicating any earthquake early warning to residents of the Marina district of San Francisco, which suffered some of the worst damage from shaking and fire outbreak.

On October 17, 2019, the thirtieth anniversary of this earthquake, the California Governor’s Office of Emergency Services unveiled a smartphone app from the University of California, Berkeley Seismological Lab that will give all Californians the opportunity to receive earthquake early warnings.

Governor Gavin Newsom, who happened to be in the Marina district at the time of the 1989 earthquake, has urged people to download the MyShake app. This app (myshake.berkeley.edu) is available on the Apple App Store and Google Play, and relies on the ShakeAlert earthquake early warning system, developed by the U.S. Geological Survey (USGS).

Continue reading

The Mw7.1 – 2019 Ridgecrest (California) Earthquake Sequence

The recent events that shook a relatively remote part of the Mojave Desert region of Eastern California provide an acute reminder of the major risk posed by earthquakes in the state. It has been a while now since California experienced a large earthquake, and the main event in this sequence – with a magnitude of Mw7.1, was the most powerful earthquake to occur in the state in twenty years.

Since then, the field of seismology as well as earth scientific measuring capabilities have undergone quite substantial improvements and innovations. Immediately after the start of the sequence, several coordinated efforts from academic, government and engineering organizations resulted in focused field surveys and the installation of additional, more densely spaced instrumentation to monitor seismicity and surface deformation, in and around the epicentral area.

So far, extraordinary amounts of high-quality data have been collected that will undoubtedly provide new insights and understanding of earthquakes in general and earthquake hazard and risk in (Southern) California, in particular. Work on these new data sets has only just started, but what have we learned so far? Here is a summary of observations and interpretations based on various (preliminary) field surveys, reports and briefings.

Continue reading

Earthquakes and Tall Buildings: Any Changes for Modeling?

A recent article entitled “A Seismic Change in Predicting How Earthquakes Will Shake Tall Buildings” that appeared in the New York Times on June 27, has generated some concern regarding the performance of tall buildings during earthquakes. The article cites statements made during the eleventh U.S. National Conference on Earthquake Engineering — which several RMS earthquake engineering experts attended, stating that there are large changes being introduced to ground motion models. Ground motion models predict the intensity of ground shaking at a site.

Continue reading

The HayWired Earthquake Scenario: An RMS View on Fire Following Earthquake Risk

New findings into the effect of a magnitude 7.0 earthquake originating from the 74 mile-long (119 kilometer) Hayward Fault in the California Bay Area, suggests that fire following earthquake alone could see more than 52,000 single-family homes burn. Earlier this month, the United States Geological Survey (USGS) released new results for their HayWired scenario, a scientifically plausible magnitude 7.0 earthquake on the Hayward fault. The hypothetical HayWired earthquake occurs at 4:18 p.m. on April 18, 2018, the anniversary of the magnitude  7.8 earthquake which struck San Francisco in 1906. The mainshock ruptures the fault along its length for about 52 miles (83 kilometers). The impact of such an event on one of the most densely populated and interconnected areas of the U.S. West Coast — with a population of about seven million people — would be disruptive.

Continue reading

Earthquakes in Oklahoma: An Update on Induced Seismicity Hazard and Risk for 2018

During 2017, Oklahoma and southern Kansas experienced Mw 3+ earthquakes more frequently than in California. Although the annual count of earthquakes in the Oklahoma/Kansas area has declined since peaking in 2015, the rate of earthquake occurrence is still extremely high. More than 50 events (Mw 3+) have occurred since the start of 2018, including events of Mw 4.6 and Mw 4.5 during the first weeks of April, with shaking strong enough to be felt in Oklahoma City.

In Oklahoma and other parts of the Central and Eastern United States, research studies have linked the increased occurrence of earthquakes to oilfield wastewater injection. Damage has mostly been minimal, but the ground shaking occurring from events greater than or equal to Mw5 could have produced extensive damage had comparable events occurred in more greatly populated areas of the state.

In 2016, the United States Geological Survey (USGS) released their first short-term forecast for seismic hazard — this was meant to capture the increased (but potentially transient) nature of this hazard, and the forecast emphasized that the seismic hazard in Oklahoma is comparable to that of California. Since the first one-year forecast in 2016, the USGS has released subsequent forecasts for 2017 and now for 2018.

Continue reading

Are You Ready for an Interim USGS NSHM Update?

RMS recently hosted a two-day workshop for the United States Geological Survey (USGS) on March 7-8, based at our Newark headquarters in California. The aim of the workshop was to both discuss and receive feedback from the scientific community on the interim update to the ongoing 2018 USGS National Seismic Hazard Map Project (NSHMP).

RMS works actively with the USGS and the community and has previously hosted USGS workshops to help facilitate scientific discussions and to improve understanding of earthquake hazard. The workshop was well attended by over 150 people from academia, the scientific community, and industry.

Continue reading

New Data, New Challenges: How RMS Updated the Version 17 North America Earthquake Models

Technology, data, and science continues to evolve when assessing and understanding earthquake risk; the new continually replaces the old. In AD 132, Chinese polymath Zhang Heng demonstrated his seismoscope, the first scientific instrument used to Continue reading

How Should Man-made Earthquakes be Included in Earthquake Hazard Models?

Oklahoma, Colorado, and Texas have all experienced unusually large earthquakes in the past few years and more earthquakes over magnitude 3 than ever before.

Over a similar time frame, domestic oil and gas production near these locations also increased. Could these earthquakes have been induced by human activity?

Figure 1: The cumulative number of earthquakes (solid line) is much greater than expected for a constant rate (dashed line). Source: USGS

According to detailed case studies of several earthquakes, fluids injected deep into the ground are likely a contributing factor – but there is no definitive causal link between oil and gas production and increased earthquake rates.

These larger, possibly induced, earthquakes are associated with the disposal of wastewater from oil and gas extraction. Wastewater can include brine extracted during traditional oil production or hydraulic fracturing (“fracking”) flowback fluids – and injecting this wastewater into a deep underground rock layer provides a convenient disposal option.

In some cases, these fluids could travel into deeper rock layers, reduce frictional forces just enough for pre-existing faults to slip, and thereby induce larger earthquakes that may not otherwise have occurred. The 2011 Mw 5.6 Prague, Oklahoma earthquake and other recent large midcontinent earthquakes were located near high volume wastewater injection wells and provide support for this model.

However, this is not a simple case of cause and effect. Approximately 30,000 wastewater disposal wells are presently operated in the United States, but most of these do not have nearby earthquakes large enough to be of concern. Other wells used for fracking are associated with micro-earthquakes, but these events are also typically too small to be felt.

To model hazard and risk in areas with increased earthquake rates, we have to make several decisions based on limited information:

  • What is the largest earthquake expected? Is the volume or rate of injection linked to this magnitude?
  • Will the future rate of earthquakes in these regions increase, stay the same, or decrease?
  • Will future earthquakes be located near previous earthquakes, or might seismicity shift in location as time passes?

Induced seismicity is a hot topic of research and figuring out ways to model earthquake hazard and possibly reduce the likeliness of large induced earthquakes has major implications for public safety.

From an insurance perspective, it is important to note that if there is suspicion that the earthquake was induced, it will be argued to fall under the liability insurance of the deep well operator and not the “act of God” earthquake coverage of a property insurer. Earthquake models should distinguish between events that are “natural” and those that are “induced” since these two events may be paid out of different insurance policies.

The current USGS National Seismic Hazard Maps exclude increased earthquake rates in 14 midcontinent zones, but the USGS is developing a separate seismic hazard model to represent these earthquakes. In November 2014, the USGS and the Oklahoma Geological Survey held a workshop to gather input on model methodology. No final decisions have been announced at this time, but one possible approach may be to model these regions as background seismicity and use a logic tree to incorporate all possibilities for maximum earthquake magnitude, changing rates, and spatial footprint.

Figure 2: USGS 2014 Hazard Map, including zones where possibly induced earthquakes have been removed. Source: USGS