Earthquake prep requires a multi-faceted approach

In the realm of natural disasters, earthquakes – unlike, say, floods, wildfires and hurricanes – are unpredictable. Despite tales about the unusual predictive behavior of animals, such as leaving their lairs, or other folklore, the U.S. Geological Survey holds that we cannot predict earthquakes and won’t be able to anytime soon. So, mitigation and preparation for your company’s facility need to come long before any seismic event. It should start when you’re scouting locations for a new facility, moving into a building, or when construction is planned for a new building.

Once you’ve established the potential of seismic activity in an area, you will want to develop a formal earthquake emergency and disaster recovery plan. Preparedness will help reduce losses, as even low-magnitude quakes can cause substantial damage to equipment, machinery and lifelines, as well as injury to employees.

Pay attention to seismic exposure when choosing a location

Location, location, location! The real estate adage applies here as well. Mitigating your earthquake exposure is all about location. That is, locating your business away from the dangers. Local or national earthquake hazard maps can tell you if your buildings are located in a region with danger of seismic activity. Retrofitting structures to withstand seismic activity can cost a great deal, so it’s best to build with earthquake risks in mind.

Avoid building:

• Near known fault zones
• Along sea coasts, which represent a danger of tsunamis
• In terrain prone to landslides
• Over landfills, which could undergo settlement or soil liquefaction

Consider the risk of locations near other elements that pose a danger during an earthquake, either from damage or because they could isolate your facility from recovery services. These include:

• Large natural gas pipelines
• Petrochemical plants
• Single-access roads
• Other single transportation access points, such as a single port 

Considerations when building

For new structures, conduct a geotechnical investigation to determine the type of foundations required even before starting design of the structure. If the structure is in an earthquake zone, additional geotechnical tests to determine soil liquefaction potential (more on that later) should be conducted. Most structural design codes, especially in seismic countries, define the soil parameters that require special strengthening measures. Along with suitable foundations (e.g., piles), soil-strengthening measures may need to be applied as well. These include lowering the groundwater table, replacing the soil, strengthening the soil by compaction or geotextiles, or other measures.

Retrofitting existing buildings

Foundation-strengthening for existing buildings includes injection grouting of the soil, micropiling, dewatering and densification, geotextiles and other measures. Based on an analysis of the structures, which should take the effective condition and material properties of the structure and its contents into consideration, have an engineer develop a retrofit strategy that lays out what elements need to be strengthened and to what degree.

These elements should be inspected regularly to help mitigate earthquake related losses: structural (load-bearing) elements, secondary (non-load-bearing) elements and organizational aspects (human factor).

Structural elements

• Have the structural designs reviewed by a qualified structural engineer; both for older structures and recent construction. Focus the evaluation on: Steel elements; Connection points; Reinforcement bars; Material properties, etc.
• If any physical changes to your facilities are planned, complete a full check of the structure to ensure compliance with the latest version of the design code.
• Consider designing the structure to the 475-year return period earthquake level (the most common standard used for assessing seismic risk). Consider secondary factors such as site amplification effects, soil liquefaction and lateral soil spread.

Non-structural elements

The highest losses (some 80% to 90%) resulting from an earthquake arise from nonstructural elements: the contents, equipment, wall partitions, etc., of a building.

• A preparation plan should include analysis by a qualified structural engineer of the stability and anchorage of machinery, storage tanks, installations and stock.
• Give emphasis to containers and piping containing flammable gases and liquids to ensure adequate design and bracing.
• Evaluate storage to reduce potential losses due to inadequate arrangement or securement of dangerous installations and goods (especially items that could cause or fuel a fire).
• Design firefighting systems (pumps, water tanks, and piping) to withstand tremors. Pump rooms should not have false ceilings as materials could damage pumps if they fail and fall.
• Regularly test and inspection seismic protection devices.

Hazards for structural features in an earthquake

Local design codes provide guidance on force levels and detailing requirements for new buildings and extensions to existing ones. Some issues to consider:

Age of the facility — Older buildings may not meet the latest structural design code requirements for force levels, detailing, dimensioning of structural elements, material properties, etc.

Architectural configurations — Unique features, such as irregular footprints or changes in vertical profile (setbacks or overhangs), require special design methodologies and detailing as their performance during an earthquake is difficult to predict.

Discontinuation of force-resisting elements — Walls and columns that are not continuous through the height of the building, and instead terminate at some level, must provide a continuous load path for the forces from all stories to the foundations. Otherwise “soft story” effects may lead to the collapse of weak stories, also known as pancaking.

Structural modifications — Seemingly simple changes to a structure (such as upgrades, changes in occupancy, installation of new equipment, modifications to internal layout through partitioning, removal of structural elements) can significantly impact the seismic performance of the building if not planned properly with the support of a structural engineer.

Roof-mounted equipment — These elements can change a structure’s dynamic characteristics, potentially affecting seismic performance.

Non-structural elements

Unreinforced masonry or concrete blocks ; Commonly used as partitions or in the construction of façades, these materials have demonstrated poor seismic performance. If not detailed properly (for example with separation gaps between the walls and the adjoining force-resisting system providing “frames” or internal reinforcement), then damage and even collapse of the walls is highly likely.

Bracing of piping — All critical piping, including piping for transport of production-critical material (e.g., gas, or of the fire-fighting system) must be braced for seismic forces. Damage to piping can result in leakage of hazardous material and/or fire following an earthquake, through disruption of fire-fighting water supply and/or release of combustible material. Ensure that all piping penetrating walls is provided with a sufficient gap to prevent shearing of the pipes during an earthquake. Fill gaps with fire-resistant foam or suitable material that can also deform under seismic loading.

Building analysis — Before undertaking any modifications or changes to any structures, or any other capital expenditure project to existing buildings, a detailed structural analysis considering the actual building configuration and condition, in terms of material properties, etc., should be undertaken in accordance with the requirements of the most recent edition of the structural design code. Material properties of existing structures can be determined using tools such as a Schmidt hammer (effective concrete compressive strength) or a Profimeter (to establish the reinforcement in the concrete).

Connections and material properties of facade elements, e.g., precast or glass — These are to be designed to withstand the expected seismic lateral deformations in accordance with the national structural design codes.

Furniture and other elements ;— Affix all loose furniture, such as bookshelves, and other elements, such as suspended ceilings or room partitions. Steel storage racks in particular carry a risk, as they can collapse, resulting in injury to staff and the loss of stored materials. Follow best practice guidelines (for example, FEMA 460) or, if available, national seismic design requirements to secure and maintain them.

Machinery and equipment — Anchor these elements to foundations. The configuration and types of anchors as well as foundation capacity should be checked by a qualified structural engineer. This issue is especially critical for tall equipment and rotating machinery.

Ensure roof-mounted equipment has been considered — This should be done during the seismic analysis of the building design. If such equipment is subsequently added to the building, the potential influence on the structure’s dynamic characteristics should be controlled by a qualified structural engineer.

“FEMA E-74: Reducing the Risks of Nonstructural Earthquake Damage – A Practical Guide” is available online here and provides valuable guidance on the reduction of seismic damage to such elements.

Consider the impact soil has on earthquake damage

Soil conditions determine the level of shaking at ground level. Softer soils, their moisture content, topographic conditions (such as proximity to a body of water body and the slope of the ground) and the presence of groundwater are just some factors that can lead to soil failure and damage to buildings. The softer the soil conditions at the site, the larger (and longer) the expected shaking.

Geotechnical investigations should be conducted before construction to determine soil conditions and to make recommendations regarding the most suitable foundation types. The investigations can also give an indication of the impact on expected shaking levels. Points to consider about soil types:

Landfills: Sites built on landfills exhibit higher shaking levels, due to amplification effects of such soft soil conditions.

Sandy and silty soils with shallow groundwater levels (say closer than 10 meters to the surface): Saturated soils, when subjected to shaking, are highly susceptible to liquefaction, where the water is ejected to the surface, weakening the soil under the foundations and resulting in building tilting, settlement or even collapse.

Sites gently sloping toward rivers or other bodies of water: Such conditions are conducive to lateral spread in which large blocks of the site shift downslope, creating large fissures in the soil and damaging foundations.

Ground accelerations are relatively large and of long duration: Local structural design codes give an indication of the design ground accelerations at a site, but not the duration of shaking, which is difficult to predict.

Liquefaction: Saturated sand or silty soil becomes almost liquid. This occurs when such soils are subject to shaking at a certain acceleration and for a relatively long time.

Protect against post-quake fires

Damage from fire is one of the biggest risks after an earthquake. Your facility can mitigate that risk with attention to proper design, especially the firefighting pump room. Unanchored pumps, suspended ceilings, inadequate gaps at pipe wall penetrations and the lack of anchorage of a day tank are some of the common issues identified in firefighting pump houses. Here are protective measures to consider:

• Brace critical piping from swaying with supporting frames, tensioned wires, etc. Pay attention to the connection of the bracing to the pipes. (Refer to FEMA P-414 for best practice guidance.)
• As mentioned earlier, ensure that critical piping has an adequate gap where it enters walls, as insufficient gaps can cause shearing of the pipe during an earthquake. Fill gaps with non-combustible fire stopping material that can deform under seismic loading, e.g., acrylic sealants.
• Anchor all critical production equipment, including fire-fighting pumps, to the foundations. Anchor bolt configuration and foundation design should be checked by a structural engineer.
• Do not connect critical piping, including firefighting water, valves and equipment, to unreinforced masonry or concrete block walls. Such components should be supported by engineered frames anchored to the concrete floor slab and load-bearing elements (columns, beams, etc.). Since these components may alter the seismic performance of the load-bearing elements, a qualified structural engineer should be consulted.
• Use seismic gas shut-off valves with caution. They should be designed for the pressures, temperatures, pipe diameters, etc., prevalent at the facility in which they are to be installed. Impact of sudden gas shutoff on the operation of the facility, the handling of gas already inside the facility, etc., are just some of the issues that should be considered during valve selection.
• Flexible connections should be provided at the connection of piping to equipment, seismic joints and other critical locations.

Protecting equipment in an earthquake

Equipment, machinery, storage racks, etc., are critical for business operations. Since the equipment and machinery needed for a building usually are not defined at the time the structure is designed, these elements do not necessarily meet the requirements to withstand earthquake forces. You can check structural design codes in seismic regions which define the design and detailing requirements for non-structural elements and their foundations. In addition, prepare a building’s content by following these guidelines (some of which were also highlighted in the section above on non-structural elements):

• Any piping connected to equipment should take seismic deformations into account, e.g., provide flexible joints, avoid connection to unreinforced masonry or concrete block walls, and be braced against swaying.
• Follow best practice guidelines or, if available, national seismic design requirements, for steel storage racks. Such structures can collapse, resulting in loss of stored material as well as injury to staff. Publicly available documents exist (e.g., FEMA 460) describing maintenance of such elements in seismic regions.
• Secure machinery and equipment with structural anchors to the foundations. The configuration and types of anchors as well as foundation capacity should be checked by a structural engineer. Tall equipment is particularly susceptible to overturning due to a high center of gravity. Confirm with the equipment supplier that the anchorage conforms to local seismic force levels, as defined in the national structural design code.
• Ensure that roof-mounted equipment has been considered in the seismic analysis during building design. If such equipment will be subsequently added to the building, the potential influence on the structure’s dynamic characteristics should be evaluated first by a qualified structural engineer.

Earthquake safety protocols for staff

The safety of employees is the highest priority during and after an earthquake. Some of the key steps in lessening the risk include:

• Ensure that critical processes are equipped with automatic shut-down devices where possible and permitted. These should be installed by qualified personnel and regularly tested.
• Design and implement fire safety measures and procedures (for example, automatic drainage into special pits equipped with firefighting systems).
• Create and maintain an emergency response team that is responsible for firefighting equipment checks, first aid training and internal and external communication.
• Ensure the emergency response team and the staff understand their responsibilities for: Evacuation procedures, shut-down sequence, etc.; Safe escape routes; Congregation points, such as clearly marked “safe zones” both indoors and outdoors, where employees can assemble in the event of an earthquake; Expected behavior, such as taking cover and not running outside during a quake; Conduct regular safety drills to ensure that all staff are aware of the appropriate procedures and all protection measures are functioning properly;
• Identify and document contact information for the local post-disaster response authorities responsible for assessing the post-event safety of structures, search and rescue, etc. These authorities can often assist with training, emergency preparedness and community level post-earthquake aid.

Visit the Earthquake Resource Hub for additional insights.