At its simplest, a seismic risk analysis is a comprehensive evaluation of a structure’s ability to withstand earthquakes. This kind of evaluation is valuable to property owners, prospective buyers and parties involved in the site’s development. Essentially, the analysis examines structural integrity, current safeguards and other factors to gauge potential losses in the wake of seismic activity.

Who Needs a Seismic Risk Analysis?

While many areas of the United States are at minimal risk of earthquakes, there are millions of people living in areas where these disasters are a distinct possibility. Many local jurisdictions in these states, including California, enforce building codes to address earthquake safety. Perhaps the most obvious reason for property owners to conduct a seismic analysis is to ensure complete compliance with the law.

A thorough analysis of potential earthquake damage is also a matter of due diligence. Parties who don’t fulfill due diligence requirements can expose themselves to serious liability and financial losses. Earthquakes can cause massive damage that exceeds the value of the building itself, so all owners should protect themselves from liability by completing seismic assessments when they could be held accountable.

Key Concepts and Definitions

Many property owners struggle to differentiate all of the different concepts and phrases used in the context of seismic analysis. Property owners should consider turning to risk analysis experts, like ATC Group Services, to help them navigate through the process.

Deterministic Analysis

A deterministic seismic analysis is conducted under the assumption that an earthquake will occur. This kind of assessment is based on an established “level of earthquake,” which can be adjusted according to local conditions. The term “level of confidence” is also used to describe the likelihood of the expected results. An 80 percent level of confidence means that this analysis would hold true in 8 out of 10 scenarios under the given conditions.

Probabilistic Analysis

Probabilistic loss analysis is calculated much differently than deterministic as it incorporates the likelihood of an earthquake occurring at all and accounts for the different possible levels of magnitude. While this method can be significantly more complex, it also provides a more direct assessment of overall financial risk for investors or owners.

Probable Maximum Loss

Probable maximum loss (PML) is a key concept in seismic risk assessments. Essentially, it describes the expected maximum damage and losses to a site. This measurement is based on deterministic analysis and is shaped by many factors, including records of historical local seismic activity in the area and estimated cost of repairing expected damages.

The Safe Way to Assess Risk

A seismic risk analysis is one of the most complex, technical and confusing practices associated with site evaluation. As specialists in due diligence and geotechnical engineering, ATC Group Services routinely supports our clients by providing complete seismic surveys and assessments delivered by a professional team. Our services include ASTM 1527-13 Phase 1 and ASTM 2018-15 assessments, as well as zoning reports, envelope studies and vapor screening.

There’s nothing we can do to stop an earthquake, but there’s dozens of ways to reduce the chances of serious structural damage and life-threatening injury. Property owners should always be mindful of seismic risk factors and seize opportunities to improve or modify their structure to stay in line with current regulations. Contact ATC today for due diligence services that you can trust.