Mar 2023

Recent Earthquakes Provide Reminder to Design and Prepare for Seismic Exposures

In the early morning of February 6th, 2023, a magnitude 7.8 earthquake with an epicenter near Nurdaği, Turkey was felt throughout central Turkey and northern Syria. Approximately 11 minutes later, a 6.7 magnitude quake hit within approximately 10 km of the first one. In the day and a half following the initial events, more than 100 aftershocks have been felt throughout the region with one having a magnitude of 7.5 and two estimated at or above 6.0.1

Seismic activity > 4.5 magnitude in Turkey and Syria in the past 7 days (Blue dot is the initial 7.8 magnitude quake),

Each earthquake has one magnitude, which is one of the concrete data points of seismic activity. Other concrete data may include the location, depth, and time. This information is great to track earthquakes, but the intensity felt by everything on earth is what this risk is all about.

The Modified Mercalli (MM) Intensity Scale was developed in 1931 by American seismologists Harry Wood and Frank Neumann. This scale uses observed effects to create an arbitrary ranking using Roman Numerals (I-X). The intensity of an earthquake is the measure of shaking at a given location and is mostly dependent on the distance from the epicenter. The surface geology and the direction of the quake also impact the intensity.1

The intensity of the initial quake in Turkey reached IX in some areas, and the aftershocks were up to VIII. The maps below are for the initial magnitude 7.8 earthquake and the 7.5 magnitude earthquake nearly 100 km north. Notice how the intensity of similar seismic activity in the same region can vary greatly.

MM Intensity of initial 7.8 magnitude quake1
MM Intensity of 7.5 magnitude aftershock1

For comparison, the Northridge earthquake in the early hours of January 17, 1994 had a magnitude of 6.7 and the intensity reached IX in several regions. Both of these major earthquakes happened in the morning, before many businesses were operating.

MM Intensity of 6.7 “Northridge Earthquake”1

Risk Logic recommends in-depth seismic evaluations at sites located in FM Global 50-250 yr. Earthquake Zones. The following maps are from FM Global Property Loss Prevention Data Sheet 1-2, Earthquakes. One way to determine the earthquake zone that a site is in is to use FM Global’s NatHaz Map.

Western Hemisphere2
Eastern Hemisphere2

Piping and equipment can move violently during an earthquake, causing breaks in connections and toppling of equipment, even when structures are not damaged. This can result in natural gas escaping through ruptured pipes, and in the creation of unexpected ignition sources. Such incidents could potentially lead to fires or explosions following an earthquake, and present a concern even in well-protected facilities, since water supplies and automatic sprinkler systems may become impaired during an earthquake. There is also a potential for a delayed response from overburdened emergency response services.

An earthquake evaluation by Risk Logic includes determining the construction type of a building, noting any irregularities that present an increased seismic risk, and checking the seismic protection of the fire protection systems, natural gas mains, racking, and other equipment or materials.

Seismic protection for the automatic fire sprinkler systems include bracing, flexibility and clearance at key locations. NFPA 13 now requires more seismic protection than was previously noted and many facilities should be reinforced to meet the current edition of NFPA 13 or FM Global Property Loss Prevention Data Sheet 2-8.

Another key part of this evaluation is assessing the human element programs for earthquake protection and response to seismic events. Regular inspections of the seismic protection are needed to confirm that the braces, straps, seismic gas shutoff valve(s), and other protection measures are still in place, or added as needed.

Preparing a plan of action for a response to an earthquake is critical to minimizing damage and the associated downtime. A preliminary inspection of the site could include inspecting the exterior of the building; fire protection, fuel gas, ignitable liquid and domestic water piping systems; racking; and, equipment for damage. The initial actions could be to isolate the damaged systems, implement the contingency plan for utility outages, and begin recovery.

If it is critical to shut down processes before damaging ground motion reaches the site, local seismic sensors or a reliable earthquake early warning system (EEWS) can be used to bring equipment to a safe condition.

In areas affected by large earthquakes, the local authorities may require structural evaluations and recertification as safe to occupy. Since there are limited inspectors and engineers, this process could take several months to complete. Section of FM Global Property Loss Prevention Data Sheet 10-2, Emergency Response outlines what a building occupancy resumption program (BORP) should include. In fewer words, a BORP includes a formal agreement with the local building department that authorizes a structural engineer to officially recertify buildings as safe to occupy. However, not all building departments sanction BORPs at this time and may need to be petitioned. One example of a BORP is the one use by the San Francisco, Department of Building Inspection.

If you need assistance in determining your exposure to seismic events, or need help developing post-earthquake duties, contact Risk Logic Inc.

Are you constructing a building, adding on to an existing building or adding equipment? Including a seismic evaluation in planned changes could prevent losses or extensive rework to mitigate an exposure. Risk Logic offers unbundled Plan Review services to review compliance with NFPA, FM Global and other standards as needed.



2 FM Global Property Loss Prevention Data Sheet 1-2, Earthquakes