Article,
Earthquakes and errors: Methods for industrial applications
Geophysics, 76 (6): WC5--WC15 (2011)
DOI: 10.1190/geo2011-0096.1
Abstract
The high accuracies and realistic confidence assessments demanded
for seismic monitoring of hydraulic fracturing work require specialist
experimental approaches. These include seismic network design based
on quantitative modeling, high-quality instrument deployments, and
accurate and detailed crustal models. Confidence estimates must take
into account uncertainties about crustal structure, which may dominate
error budgets. Earthquake size should be expressed in terms of scalar
seismic moment or the associated moment magnitude MW, which is related
to fundamental physical source processes, and not as traditional
earthquake magnitudes. Representing earthquake mechanisms in terms
of seismic moment tensors allows for processes such as volume changes
and complex types of shearing that are important in hydrocarbon and
geothermal reservoirs. Traditional fault-plane solutions are based
on simplifying assumptions such as shear slip on a planar faults,
and isotropic crustal structures, which may introduce large uncertainties.
Quantitative assessment of confidence regions for moment-tensor source
mechanisms, a newly emerging field, is important for distinguishing
computational artifacts from real physical phenomena. We review methods
currently available for realistic error estimation for earthquake
locations and moment tensors, with particular emphasis on surface
sensor arrays in geothermal areas.
