GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundari... more GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundaries, and striking intraplate deformation. Although much has been learned using by geologic GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundaries, and striking intraplate deformation. Although much has been learned using by geologic plate motion models based on magnetic anomalies, transform azimuths, and
Space-based geodesy can shed significant light on the processes causing intraplate earthquakes by... more Space-based geodesy can shed significant light on the processes causing intraplate earthquakes by constraining the rate at which the crust accumulates the elastic strain that will be released in future earthquakes. For some years, we and others have been using GPS data from sites in eastern North America to investigate deviations from plate rigidity that reflect intraplate strain. Successive studies
With a CMT moment of 1.84E29 dyn*cm, the 2010 Maule, Chile earthquake is the second largest since... more With a CMT moment of 1.84E29 dyn*cm, the 2010 Maule, Chile earthquake is the second largest since the inception of modern digital recording, and the fourth (or fifth) largest to ever be quantified. Among the very selective group of such "mega-events", several earthquakes (1960 Chile, 2004 Sumatra, 1964 Alaska) have been shown to feature an ultra-slow component to their source, expressed as an increase in moment with the period of measurement, and the question has been raised of whether this behavior is a universal feature of the Earth's largest earthquakes. We study the source of the Maule earthquake through a quantification of the Earth's modes in the period range 600 - 3200 s, using the algorithm of Stein and Geller [1977] to model the full splitting of the gravest modes. Our results indicate that all spectral lines are compatible with the CMT moment (within a factor of 15%), and thus preclude the existence of a slow component to its source. In this respect, the event is most comparable to the 2005 Nias earthquake which had a similar moment, and incidentally, also featured a bilateral rupture. It also differs most significantly from the neighboring great 1960 event which was characterized by an extremely slow precursory component to its source.
Volcanic eruptions are among Earth's most spectacular surface phenomena. However, attemp... more Volcanic eruptions are among Earth's most spectacular surface phenomena. However, attempts to understand their basic physics face the challenge that the key processes occur at great depth and are difficult to observe. Thus volcanologists have been interested for ...
A common student response to quantitative questions without obvious answers is "I have no idea." ... more A common student response to quantitative questions without obvious answers is "I have no idea." Often these questions can be addressed by Fermi estimation, in which a difficult-to-estimate quantity is estimated by combining order of magnitude estimates of easier-to-estimate quantities. Although this approach is commonly used for numerical estimates, it can be applied to issues combining science and policy. Either application involves dividing an issue into tractable components and addressing them separately. To learn this method, our natural hazards seminar considered a statement by the Illinois Emergency Management Agency that homeowners should secure water heaters to prevent them from being damaged by earthquakes. We divided this question into subtopics, researched each, and discussed them to reach a synthesis. We estimated the net benefit: the difference between the expected value of damage and the cost of securing. This benefit is positive, indicating that securing is worthwhile, only if the probability of damage during the heater's life is relatively large, approximately 1%-10%. To assess whether the actual probability is likely to be this high, we assume that major heater damage is likely only for shaking with modified Mercalli intensity VIII ("heavy furniture overturned") or greater. Intensity data for 200 years of Illinois earthquakes show that this level was reached only in the southernmost part of the state for the 1811-1812 New Madrid earthquakes. As expected, the highest known shaking generally decreases northward toward Chicago, consistent with the fact that we find no cases of earthquake-toppled water heaters in Illinois. We compared the rate of return on securing a water heater in Chicago to buying a lottery ticket when the jackpot is large and found the latter a better investment. This project let us explore ideas that might otherwise have seemed abstract and difficult to grasp, and suggests that other courses might consider similar projects.
Siam Asa Journal on Uncertainty Quantification, 2013
Uncertainty issues are crucial in assessing the risk posed by natural hazards and developing stra... more Uncertainty issues are crucial in assessing the risk posed by natural hazards and developing strategies to mitigate their consequences for society. The challenges are illustrated by the giant earthquake that struck Japan's Tohoku coast in March, 2011, which was much larger than had been predicted by sophisticated hazard models and so caused a tsunami that overtopped 5-10 m seawalls, causing more than 15,000 deaths and $210 billion damage. Deciding whether to rebuild these defenses and more generally what strategies to employ against such rare events depends on estimating the balance between the costs and benefits of mitigation. Making such estimates is a complex challenge at the intersection of geoscience, mathematics, and economics. The major uncertainty is the probabilities of the rare, extreme events and the waiting or recurrence times between them. The probabilities of these events are difficult to estimate because the physics of earthquake recurrence is not adequately understood, and the short geologic record provides only a few observations. We present a general stochastic model in which the probabilities either are constant with time or depend on the previous history. We then develop models for two hazard policy issues facing Japan. One uses a stochastic model to select an optimum mitigation strategy against future tsunamis by minimizing the sum of the expected present value of the damage, the costs of mitigation, and a risk premium reflecting the variance of the hazard. We also consider whether new nuclear power plants should be built, using a deterministic model that does not require estimating essentially unknown probabilities. These models can be generalized to mitigation policy situations involving other natural hazards.
GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundari... more GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundaries, and striking intraplate deformation. Although much has been learned using by geologic GPS geodesy can improve understanding of plate motions, diffuse and poorly-located plate boundaries, and striking intraplate deformation. Although much has been learned using by geologic plate motion models based on magnetic anomalies, transform azimuths, and
Space-based geodesy can shed significant light on the processes causing intraplate earthquakes by... more Space-based geodesy can shed significant light on the processes causing intraplate earthquakes by constraining the rate at which the crust accumulates the elastic strain that will be released in future earthquakes. For some years, we and others have been using GPS data from sites in eastern North America to investigate deviations from plate rigidity that reflect intraplate strain. Successive studies
With a CMT moment of 1.84E29 dyn*cm, the 2010 Maule, Chile earthquake is the second largest since... more With a CMT moment of 1.84E29 dyn*cm, the 2010 Maule, Chile earthquake is the second largest since the inception of modern digital recording, and the fourth (or fifth) largest to ever be quantified. Among the very selective group of such "mega-events", several earthquakes (1960 Chile, 2004 Sumatra, 1964 Alaska) have been shown to feature an ultra-slow component to their source, expressed as an increase in moment with the period of measurement, and the question has been raised of whether this behavior is a universal feature of the Earth's largest earthquakes. We study the source of the Maule earthquake through a quantification of the Earth's modes in the period range 600 - 3200 s, using the algorithm of Stein and Geller [1977] to model the full splitting of the gravest modes. Our results indicate that all spectral lines are compatible with the CMT moment (within a factor of 15%), and thus preclude the existence of a slow component to its source. In this respect, the event is most comparable to the 2005 Nias earthquake which had a similar moment, and incidentally, also featured a bilateral rupture. It also differs most significantly from the neighboring great 1960 event which was characterized by an extremely slow precursory component to its source.
Volcanic eruptions are among Earth's most spectacular surface phenomena. However, attemp... more Volcanic eruptions are among Earth's most spectacular surface phenomena. However, attempts to understand their basic physics face the challenge that the key processes occur at great depth and are difficult to observe. Thus volcanologists have been interested for ...
A common student response to quantitative questions without obvious answers is "I have no idea." ... more A common student response to quantitative questions without obvious answers is "I have no idea." Often these questions can be addressed by Fermi estimation, in which a difficult-to-estimate quantity is estimated by combining order of magnitude estimates of easier-to-estimate quantities. Although this approach is commonly used for numerical estimates, it can be applied to issues combining science and policy. Either application involves dividing an issue into tractable components and addressing them separately. To learn this method, our natural hazards seminar considered a statement by the Illinois Emergency Management Agency that homeowners should secure water heaters to prevent them from being damaged by earthquakes. We divided this question into subtopics, researched each, and discussed them to reach a synthesis. We estimated the net benefit: the difference between the expected value of damage and the cost of securing. This benefit is positive, indicating that securing is worthwhile, only if the probability of damage during the heater's life is relatively large, approximately 1%-10%. To assess whether the actual probability is likely to be this high, we assume that major heater damage is likely only for shaking with modified Mercalli intensity VIII ("heavy furniture overturned") or greater. Intensity data for 200 years of Illinois earthquakes show that this level was reached only in the southernmost part of the state for the 1811-1812 New Madrid earthquakes. As expected, the highest known shaking generally decreases northward toward Chicago, consistent with the fact that we find no cases of earthquake-toppled water heaters in Illinois. We compared the rate of return on securing a water heater in Chicago to buying a lottery ticket when the jackpot is large and found the latter a better investment. This project let us explore ideas that might otherwise have seemed abstract and difficult to grasp, and suggests that other courses might consider similar projects.
Siam Asa Journal on Uncertainty Quantification, 2013
Uncertainty issues are crucial in assessing the risk posed by natural hazards and developing stra... more Uncertainty issues are crucial in assessing the risk posed by natural hazards and developing strategies to mitigate their consequences for society. The challenges are illustrated by the giant earthquake that struck Japan's Tohoku coast in March, 2011, which was much larger than had been predicted by sophisticated hazard models and so caused a tsunami that overtopped 5-10 m seawalls, causing more than 15,000 deaths and $210 billion damage. Deciding whether to rebuild these defenses and more generally what strategies to employ against such rare events depends on estimating the balance between the costs and benefits of mitigation. Making such estimates is a complex challenge at the intersection of geoscience, mathematics, and economics. The major uncertainty is the probabilities of the rare, extreme events and the waiting or recurrence times between them. The probabilities of these events are difficult to estimate because the physics of earthquake recurrence is not adequately understood, and the short geologic record provides only a few observations. We present a general stochastic model in which the probabilities either are constant with time or depend on the previous history. We then develop models for two hazard policy issues facing Japan. One uses a stochastic model to select an optimum mitigation strategy against future tsunamis by minimizing the sum of the expected present value of the damage, the costs of mitigation, and a risk premium reflecting the variance of the hazard. We also consider whether new nuclear power plants should be built, using a deterministic model that does not require estimating essentially unknown probabilities. These models can be generalized to mitigation policy situations involving other natural hazards.
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Papers by Seth Stein