Geoscience Reference
In-Depth Information
Finally, step 4 involves estimating the probability that structures and people are affected
(cell 4A). Analytical methods for seismic risk analysis (cell 4B) are well established for
tectonic earthquakes, and these should be applicable to induced earthquakes. The methods
will not depend on technology (cell 4C), because a structure's response does not depend
on how the shaking was generated. However, the methods do depend on region (cell 4D);
structures outside of California and Alaska are generally not designed to withstand high
levels of ground shaking, and people in aseismic regions may be less tolerant of low-level
shaking than those who have previously felt natural earthquakes. Deeper earthquakes will
have an influence on the numbers of structures and people affected (cell 4E) if the associated
earthquake shaking covers a wide region and affects more structures and people.
Table 5.2 summarizes steps that can be taken to estimate hazard and risk for individual
energy projects. The specific statistical data that need to be collected, and analytical methods
that need to be modified from other fields, are summarized in column B. Each of the sta-
tistical or analytical methods in column B will calculate the probability indicated in the
corresponding cell in column A, and these calculations will depend on the corresponding
cells in columns C, D, and E. For instance, statistical data on M ≥ 2 earthquake generation
(cell 1B) need to be collected and analyzed by energy technology, volume of fluid, injection
pressure, rate of injection, etc. An unstated assumption in Table 5.2 is that data are to be col-
lected for new energy projects in areas that are known to have a history of induced seismicity,
as well as existing projects. The reason is that, going forward, we presumably are interested
in estimating hazard and risk from induced seismicity caused by further expansion of energy
production, not by existing energy production. However, data from existing projects will
allow forecasts of induced seismicity for industries as a whole. The distinction is important:
seismicity induced by a new injection or disposal well will differ from seismicity induced by
a well that has been in production for years, where crustal stresses may have equilibrated.
Note that steps 1 through 3 apply regardless of whether the potential induced seismicity
will occur in areas of high population or sparse population. Step 4 determines the effect
on structures and people, and this effect of course depends on the location with respect
to structures at risk and people. Induced seismicity could be caused in a region of sparse
population, affecting few people, but could affect dams, bridges, or power plants, with large
concurrent costs.
These steps, if developed, can be used in three important ways:
First, by compiling statistics on earthquake generation by technology and character-
istics (cell 1C), insight can be gained on what combinations of volumes, pressures, rates
of injection/extraction, and so on lead to higher probabilities of induced seismicity. This
insight can be used to create well-documented, data-based input to best practices protocols
(see also Chapter 6).
Second, energy technology development, whether through public or private efforts,
will have data with which to make decisions to minimize induced seismicity effects on
 
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