Volcanic Eruptions and Their Repose, Unrest, Precursors, and Timing (2017) / Chapter Skim
Currently Skimming:
3 Forecasting Eruptions
3 Forecasting Eruptions
Pages 53-68
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 53... ...
Achieving a paradigm shift, from pattern primarily rely on the geologic record of past eruptions. recognition to model-based forecasting, will require Long-term forecasts assess eruption potential and haz- improved constraints on plumbing system geometry ards over the lifespan of a volcano and are independent and nonlinear material response, and improved under of short-term forecasts.
|
From page 54... ...
However, t successfully forecast based on patterns of precur- many other volcanoes, particularly those that erupt sory seismic tremor and localized deformation that violently, have had limited or no historical eruption consistently preceded events (Malone et al., 1981; observations and few quantitative measurements. In Swanson et al., 1983)
|
From page 55... ...
At 17:20 the local volcano science community was notified of a potential eruption, around the time volcanic tremor was recorded at the closest seismometer. At 17:30, shortly after the same strainmeter began showing a signal nearly identical to that of the 1991 eruption, a warning was issued to the National Civil Protection Agency (Stefánsson, 2011)
|
From page 56... ...
, 1995–? were later accompanied by lava-dome growth and pyroclastic as increased seismicity and inflation, were successfully used flows that forced evacuation of the southern half of the island to anticipate the most dangerous times and the most likely and ultimately destroyed the capital city of Plymouth, causing timing of dome-collapse pyroclastic density currents.
|
From page 57... ...
-1 20 Event 12 10 0 9 8 7 6 5 4 3 2 1 0 -1 Frequency (Hz) 20 Event 13 10 0 9 8 7 6 5 4 3 2 1 0 -1 20 Event 14 10 0 9 8 7 6 5 4 3 2 1 0 -1 Minutes Before Eruption FIGURE 3.1 Changes in the rate of earthquakes and the frequency content of their seismic waves are used to forecast eruptions at well-monitored volcanoes.
|
From page 58... ...
14-16 km (i) 10 5 J M M J S N J M M J S N 2005 2006 FIGURE 3.2 The ratios of chemical species in volcanic gas are sensitive indicators of magma ascent, and so can be used to forecast eruptions.
|
From page 59... ...
, with the caveat that the tion on the pressure, temperature, volatile content, and record of observed eruptions is biased toward small to composition of the deep magmatic system feeding the moderate events at frequently active volcanoes, whereas eruption. Active and passive source seismic experiments the prehistoric geologic record is biased toward larger with high-density coverage will continue to improve eruptions (Kiyosugi et al., 2015)
|
From page 60... ...
This sealing process can be manifested by fluctuations Tephrachronology and deposit mapping are the in gas emissions, tilt, or long period seismicity (e.g., most important tools for understanding magnitudes Cruz and Chouet, 1997; Fischer et al., 1994; Johnson and frequencies of past eruptions and for inferring et al., 2014; Nishimura et al., 2012; Rodgers et al., 2015; potential future activity, including large-magnitude, Stix et al., 1993; Voight et al., 1998)
|
From page 61... ...
Similarly, numerical models that simulate transport phenomena -- emerging remote sensing technologies, including near such as the development of eruption plumes, pyroclastic real-time four-dimensional morphological mapping flows, tephra fallout, lava flows, and lahars -- given that and new space-borne lidars (e.g., Hughes et al., 2016) , a specific type of eruption has occurred (Section 2.3)
|
From page 62... ...
Short-term forecasts use models are used to estimate how far volcano products geophysical or geochemical data to forecast potential such as lava flows and tephra will extend from eruptive dike intrusion and vent locations. However, even with vents, given an eruption of a specific magnitude and high-resolution networks of instruments, the location style.
|
From page 63... ...
Physical–chemical models of ash dispersal, lava flow, and, to lesser degree, • Documenting ambient noise and shear-wave pyroclastic density current inundation are more advanced splitting observations of wave speed changes prior to and so offer more near-term promise for this approach. eruption by conducting experiments at more volcanoes, and correlating changes with changes in deforma- Expanding Monitoring Efforts: tion and other geophysical measurements such as grav- On the Ground and from Space ity and electrical resistivity; Tremendous strides have been made in develop 2 For ing techniques to forecast eruptions in the short term.
|
From page 64... ...
. Calculating N probabilities based on alternative models leads to weighted ensemble models, M, which are used to evaluate hazard probabilistically, often for a specific location using a hazard curve (lower right)
|
From page 65... ...
. Circled areas outline lava flows and eruptive fissures, inferred from a radar image on September 6, 2014.
|
From page 66... ...
One way to balance NASA–Indian Space Research Organisation synthetic the tradeoff between long repose between major erupaperture radar mission provides 12-day repeat passes, tions and our need to mitigate their dire consequences which are too coarse for monitoring or documenting is to work toward sparse ground-based monitoring the evolution of eruptions. With a larger constellation of all potentially active volcanoes (such as one or two of satellites, this repeat time could be reduced.
|
From page 67... ...
of diverse observations for immediate use, and • What physical parameters of volcanic maintain them over the long term. systems are most helpful in indicating which • Aim for seismic monitoring of each of those systems are most likely to erupt in potentially active volcano and routine daily coming decades?
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.