Paths Forward to Understanding and Managing Induced Seismicity in Energy Technology Development - Induced Seismicity Potential in Energy Technologies - page 124

TABLE 5.1 Probability of Damage Increases with Number of Wells

Expected Number of Wells
Causing Moderate+ Damage

Total Number of Wells ( N ) [P M ] N wells

1 1% 0

5 5% 0

10 10% 0

100 63% 1

1,000 99.9% 10

ability of at least one observation of moderate+ damage given that N wells are in operation
can be calculated 2 as

[P M ] N wells = probability of 1 or more moderate+ damaging motions for N wells
= 1 - (1 - P M ) N

This probability increases with the number of wells N (for P M = 1%), as shown in Table 5.1.

This example illustrates that, as an industry begins operation with a few wells, there
might be no apparent problem with induced seismicity. As the industry expands to 100,
1,000, or more wells, there can be a significant likelihood that induced seismicity will
cause damage to structures somewhere, as a result of the large number of earthquakes and
ground motions that are induced, even though the probability of any one well producing
such ground motions is small.
Tectonic earthquakes cause some level of earthquake risk for buildings, primarily in areas
like California with relatively frequent events. Seismic building codes provide some level
of protection but are not a guarantee against earthquake damage. In other regions, build-
ing codes provide lower levels of seismic protection, and earthquakes (whether tectonic or
induced) may cause damage, depending on the level of ground motion associated with them.

QUANTIFYING HAZARD AND RISK

Several steps can be taken to quantify hazard and risk. As described in the previous
section, the quantification of hazard and risk requires probability assessments, which may be

2 This is a special case of the Bernoulli distribution with N independent trials and probability P M of occurrence of
the phenomenon of interest (moderate+ damage). The probability of at least one observation of this damage is 1 minus the
probability of no observations of this damage, given N independent trials. Any dependence among ground motions for a
given technology can be examined as part of the hazard assessment step identified in the section Quantifying Hazard and
Risk (this chapter), in particular step 3 in Table 5.2.