Seismic monitoring of buildings and infrastructure
A permanent network of accelerometers records the structure's response during the earthquake. The data are available within the first hours, and the post-event report signed by a structural engineer turns them into an outcome you can act on.
What seismic monitoring changes
The problem
After an earthquake, the condition of a building is assessed by eye, and the eye picks up apparent damage. Damage in joints, connections and elements concealed by finishes requires investigation, and in the meantime caution prevails: operations stay suspended longer than necessary.
The solution
BBOX 2.0 records the actual response of the structure during the earthquake. Within the first hours, engineers have measured accelerations, displacements and drift, and MOSI's post-event report states whether there is damage, how severe it is and where it is located: the decision to resume rests on objective evidence, and inspections go where they are needed.
What is seismic monitoring
Seismic monitoring is the measurement of a structure's response during an earthquake, using accelerometers permanently installed at the foundation and on the floors. The recorded accelerations yield displacements, interstorey drift and the amplification of motion up the height of the structure: the quantities a structural engineer uses to assess whether the event caused damage and in which part of the structure.
It is an event-based mode: recording starts when acceleration exceeds a set threshold. Earthquakes are the main reference, and on the same principle the system records impacts, extreme wind and any exceptional dynamic load that exceeds the threshold.
For this function BBOX has long been described as the black box of buildings: what the structure went through during the event stays on record and becomes the objective basis for the assessment that follows.
After an earthquake, decisions are made within hours
In the hours after a shock, people decide whether to re-enter, whether to resume operations and which parts to inspect first. In Italy, the public emergency inspection, carried out with the AeDES form (the national post-earthquake damage and usability survey), produces a rapid, provisional judgement; in a workplace, the decision to resume operations rests with the employer.
What if the building is earthquake-resistant?
Seismic design protects people, and at the life-safety limit state the Italian building code (NTC 2018, §3.2.1) accepts significant damage to structural components and failure of non-structural components and building services. A building can therefore come through the event damaged.
Public networks take measurements for the same reason. The Observatory makes it possible to assess the damage an earthquake causes to the monitored structures; in California, building records have been used to assess building integrity after earthquakes and to revise design codes.
After the event, MOSI delivers a report you can act on
MOSI processes the recorded data and delivers a post-event report, interpreted and signed by a licensed structural engineer who takes professional responsibility for it. MOSI works on an ongoing basis with structural engineering firms: keeping measurement and assessment in separate hands makes the document a verifiable technical deliverable.
It is the document the owner or operator uses to decide whether to keep the structure in service, where to focus inspections and which works to start. Where catastrophe insurance is mandatory, as it is for businesses in Italy, a measurement of the earthquake's effect on the structure makes the difference between damage that is documented and damage that has to be proven.
On request, MOSI also prepares a technical report on post-earthquake structural usability, separate from the measures that fall to the competent authorities.
- Accelerations recorded at the base and on the floors
- Displacements and interstorey drift compared with design limits
- A clear outcome: no damage detected, or possible damage
- Severity and location of the effects detected
- Stated methodology
- Signature of the structural engineer
How the system records an earthquake
The trigger threshold is set for each sensor and can be changed remotely, so sensitivity adapts to the structure and to the ordinary vibrations of the site, such as machinery and traffic. All channels share the same time reference: this is what makes drift calculable, because it compares the same instant on different floors.
The sensors are fixed to the structure without altering the load-bearing structure, including on existing buildings.
For reference, the ANSS guidelines of the US Geological Survey for seismic monitoring of engineered civil systems specify at least 30 seconds of pre-event recording, at least 80 seconds of post-event recording and at least 200 samples per second. In BBOX 2.0 durations are configurable and sampling reaches 1000 Hz.
Accelerations, displacements, drift: what is measured
Peak accelerations
Displacements
Interstorey drift
Inclination
Seismic isolators: performance measured during the event
In a structure with isolators, the system's performance shows during the earthquake. The Italian building code (NTC 2018, §7.10.7) requires a maintenance plan with periodic checks recorded for the entire life of the building; instrumental measurement adds to those checks the performance recorded during the event.
With sensors above and below the isolation plane, the ratio between the accelerations measured on the two sides quantifies how much motion the device held back, bearing by bearing. Comparing different bearings shows whether the system worked uniformly across the plan and where to focus inspection.
Among the representative installations is the new INRCA hospital in Camerano, Italy: 32 accelerometric sensors that, when an event occurs, verify the dissipative effectiveness of the isolators by comparing accelerations across the isolation plane.
Frequently asked questions on monitoring seismically isolated structures →Where a rapid response matters most
- Industrial and logistics sites
The decision to stay in production after the event rests on measurements of the building's response, as at Florim Ceramiche's Fabbrica 4.0 in Fiorano Modenese, Italy.
- Critical infrastructure
Hospitals and emergency facilities that must stay operational in the critical hours.
- Residential buildings
A rapid assessment of the condition of apartment buildings after an earthquake, to protect residents.
- Office and retail buildings
Resumption of operations at the premises, decided on measured data.
- Heritage buildings
The seismic response of towers and bell towers, read together with their inclination.
- Bridges and viaducts
Earthquakes and impacts recorded on the structure, supporting the operator's inspections.
The same sensors also track degradation over time
In the base configuration of BBOX 2.0 the same sensors also perform Structural Health Monitoring. SHM works in ordinary service, even in the absence of earthquakes or other exceptional events: the ambient vibrations produced by wind, traffic and machinery are enough to measure how the structure behaves and to track its slow degradation over time. The history recorded in ordinary years is also the reference for reading the condition of the structure after an event.
Technical and regulatory references
- Italian Civil Protection Department (Dipartimento della Protezione Civile), Seismic Observatory of Structures (Osservatorio Sismico delle Strutture).
- California Geological Survey, California Strong Motion Instrumentation Program, data as of September 2024.
- US Geological Survey, Guideline for ANSS Seismic Monitoring of Engineered Civil Systems, Open-File Report 2005-1039.
- Italian Ministerial Decree of 17 January 2018, Technical Standards for Construction (Norme Tecniche per le Costruzioni, NTC 2018), §3.2.1, §7.3.6.1 and §7.10.7.
- FEMA P-58-1, Seismic Performance Assessment of Buildings, 2018. FEMA E-74, Reducing the Risks of Nonstructural Earthquake Damage.
- Italian Law no. 213 of 30 December 2023, art. 1, paragraphs 101-111 (mandatory catastrophe insurance for businesses).
Let's design seismic monitoring for your structure
The number and position of sensors, trigger thresholds and report content depend on the structure and on the decisions it will need to support. The MOSI team defines the configuration with you.
Request a technical consultationContinue reading
- How continuous structural monitoring works: SHM and post-event monitoring
- BBOX 2.0: sensors, datalogger and the consultation platform
- BBOX 2.0 installations on buildings, bridges and heritage sites
- Frequently asked questions on structural monitoring
- MOSI Srl: who we are and why we build monitoring systems
- Insights on regulation and the condition of the built environment