The GeoNet system provides the magnitude rating as measured by a country-wide network of seismic stations, and the data from all available stations are then combined to give an overall value for the event. The “reported shaking” is calculated from feedback from website visitors who choose to submit a “felt report”. This “felt report” is based on the perception of those who submit reports experience in the shake, and they can vary significantly.
GeoNet provides world-class information about the measurement of the event, the earthquake itself, along with what people have perceived in their buildings, at their locations. But due to sparse instrument measurements, it is limited in ability to advise tell you what shaking actually occurred at a specific location.
Our solution, Sentinel, is a global first for urban earthquake effects management. Sentinel delivers Earthquake Response and Resilience as a service for best-practice Health and Safety, eliminating unnecessary business closures and accelerating economic recovery. The unique end-to-end service measures shaking and generates, in real time, a ground response spectrum for every individual building covered by our service. Sentinel then directly compares ground shaking against the NZ Building Code design demand of your individual and instantly alerts you to your building’s status, sending directly to offices, sites, assets, alerts, smartphones and computers.
The key is in deploying earthquake measurement sensors to take the measurement that then drives your earthquake response process, removing the human factor and basing the response process in sound engineering metrics.
To help you understand this technology, we've created a situation based on a real earthquake that illustrates what Sentinel does, and how you can use the information to make decisions about your building and your business.
You are:
The property manager of a building on the corner of St Asaph and Madras Streets in the Christchurch CBD
The Event
An earthquake beneath Christchurch, 8:43 am Monday July 22, 2019
The Situation
People are just arriving for work. The shaking is enough to alarm some people. Others are standing around wondering what they should do - can they enter the building safely?
Let's look at GeoNet's report on this particular quake:
Here is a breakdown of the key results GeoNet has provided:
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Magnitude: |
3.9 |
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Moderate shaking: |
What impact has it had on the building? |
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Felt: Variable |
Some people thought it was a light shaking, others reported that it was strong, because Felt reports are based on individuals' perception and everyone has a different idea of what they felt. |
Let’s take a closer look at the GeoNet report:
GeoNet had a total of 75 felt reports from people near the location of the earthquake, their reports of the shaking vary.
Starting with the measurement of the magnitude (3.9) from seismographs around the region, the report also provides basic information based off other people’s perception of the shaking. The information provided doesn’t include the effect of the quake on your building on the corner of St Asaph / Madras streets and is more general in nature, you need to infer the shaking at your building and any risk that presents.
Now let's assume you're a Sentinel user, and you have immediate access to the data it provides. Sentinel relates the shaking acceleration (intensity) and how rapid the shaking is (frequency), to how the building behaves. Sentinel’s Ground Response Spectrum is easily related to building design strength in ways other measurements cannot.
Based on the expected size of large earthquakes, the NZ Building Code defines limit state curves of shaking intensity vs. frequency. The curves are scaled based on soil type, building importance level and percentage of code.
Sentinel provides instant and precise results with alerts to your phone, laptop or other systems. It directly measures ground shaking at hundreds of points. It then instantly compares the point-by-point shaking to every individual building’s design limits using best-practice and well-proven spectral analysis techniques. Results are sent immediately to the building occupants, the building manager and the structural engineer.
Now, let’s review what Sentinel reported on this earthquake:
Based on the above, I know what the ground shaking is at my building, from a nearby sensor.
By clicking on the map I know what it means:
MODERATE: Generally felt outside and by almost everyone indoors. Most sleepers awakened and a few alarmed. Small objects shifted or overturned. Some glassware and crockery breakage, doors swing open and shut.
I can also know what’s happened to my friend’s and family by clicking on their location
And what about my building?
A further breakdown of the information Sentinel provided:
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Ground shaking for your building, from the nearest sensor: |
In this case, the shaking was MODERATE. This means it was felt outside and by almost everyone indoors. Small objects shifted or overturned. There was some glassware and crockery breakage, with doors swinging open and shut. |
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The comparison of the ground shaking to the building’s design strength: |
It was 19%, which means it remains in the WHITE zone in horizontal and vertical planes. The AMBER limit is 25%, which means that damage is unlikely and the building should remain fully operational. |
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Your decision: |
Business as usual. No need to evacuate |
Sentinel is the technology that ensures you make the right call following an event. Equipped with the information specific to your building when you really need it, delivered in a variety of ways to all the stakeholders you need.
Sentinel is monitoring more than 500 buildings and guiding building occupancy that impacts hundreds of thousands of people. Sentinel’s subscription service covers all of New Zealand. No maintenance. No building owner permission. No hassle. No delay.
Are you responsible for your people’s safety and your organisation’s continuity? Then get in touch with us for a free demo to find out how Sentinel can provide the assurance you need.