Earthquake Alarm and Measurement

The Earthquake

We do not know when and where earthquake will struck. However, with the technology of today, at least we can readily know of the earthquake activity even if the intensity is below the grasps of our senses and feelings.

Let us have some earthquake short tutorial

Did you know that during an earthquake, there is normally 2 waves that arrives. The first one is called a P-Wave, and the 2nd and most destructive is the S-Wave. Graph below illustrates the P-wave and S-wave arrival. See British Geological Survey for more details.

Three of this reading from different geographical locations determine the epicenter of the earthquake. See the blog on locating the earthquake

As a summary, you don't want to be in a dangerous situation when S-Wave (or the strongest) comes.

Article below shows how earthquake is measured. This article was taken from British Geological Survey Website

• A seismogram is a record of the seismic waves from an earthquake.

• A seismograph or seismometer is the measuring instrument that creates the seismogram.

• Almost all seismometers are based on the principle of inertia: a suspended mass tends to remain still when the ground moves.

• The relative motion between the suspended mass and the ground will then be a measure of the ground’s motion.

• On a seismogram from an earthquake, the P-wave is the first signal to arrive, followed by the slower S-wave, then the surface waves.

• The arrival times of the P- and S-waves at different seismographs are used to determine the location of the earthquake.

• Given that we know the relative speed of P- and S-waves, the time difference between the arrivals of the P- and S-waves determines the distance the earthquake is from the seismograph.

Measuring Earthquake

Earthquake is represented by several measurements in magnitude and intensity. The most common are:

• Richter Scale
• Mercalli Scale
• Shindo Scale

Detailed history of the earthquake scale can be found in Wikipedia.

The Shindo intensity scale is widely used in Japan which is based on instrument readings. The basis of unit is based on gals, centimeter per second square, or g.

0.01 m/s² = 1 Gal 

1 cm/s² = 1 Gal

1 g = 981 Gal

1 g = 9.81 m/s²  

Read the article in Wikipedia regarding the Peak Ground Acceleration, relationship of Instrumental Scale and to the what people felt, and correlation with Mercalli Scale. Below are the Mercalli Scales, corresponding g reading, and the perceived effect.

This units are used in building construction as a guide to the building earthquake resistance, and as a reference data of Structural Engineers to declare the structural soundness of the buildings.

Measurement and Alarm

Awhile ago, an earthquake struck Cebu Philippines with a magnitude of 7.2 in the Richter Scale. See how the magnitude 7.2 is perceived in youtube below:

The magnitude 7.2 in Richter Scale is equivalent to Mercalli VIII with a g of 0.34 to 0.65 as shown in the table below

Instrumental Intensity	Acceleration (g)	Velocity (cm/s)	Perceived Shaking	Potential Damage
I	< 0.0017	< 0.1	Not felt	None
II-III	0.0017 - 0.014	0.1 - 1.1	Weak	None
IV	0.014 - 0.039	1.1 - 3.4	Light	None
V	0.039 - 0.092	3.4 - 8.1	Moderate	Very light
VI	0.092 - 0.18	8.1 - 16	Strong	Light
VII	0.18 - 0.34	16 - 31	Very strong	Moderate
VIII	0.34 - 0.65	31 - 60	Severe	Moderate to heavy
IX	0.65 - 1.24	60 - 116	Violent	Heavy
X+	> 1.24	> 116	Extreme	Very heavy

Note: Table taken from Wikipedia (URL: http://en.wikipedia.org/wiki/Peak_ground_acceleration)

As a summary, the reading in Cebu are as approximately follows based on different scale

Oct 15,2013, magnitude 7.2 in Richter Scale. Equivalent to:

• Mercalli VIII
• g 0.34 - 0.65
• velocity of 31 - 60
• Gals 333.54 to 637.65
• Shindo Scale 6 upper

Alarms / Announcement, AllTechSolution Capability

In the beginning, we explained that there are 2 waves. Sometimes, the first wave cannot be felt, but it doesn't mean that the 2nd wave will not be destructive.

What happened in the video is that the 2nd wave was proven to be destructive because of the number of buildings that fell down. Just imagine if a number of people were in the building and crushed to the ground like the one that happened in Baguio City Philippines in 1990. That would be tragic on the 2nd time around.

We have had our taste of experience in the 1990 event, and this became our guiding principle to bring in the right product to the people for safety purposes.

AllTechSolution has brought a product to Philippines known as Earthquake Alarm/Monitoring System. See photo below:

The integrated unit is combination of SW-72R Seismic Monitor and SW-74 Seismic Processor. The SW-72R Seismic Monitor continuously scan the ground acceleration at 100 times a second. The data provided by SW-72R is a number that a layman can easily understand.

When an earthquake occurs, it shakes the ground. This shaking is detected by the SW-72R at 100 times a second at 16 bits resolution. Observing the SW-72R and SW-74SI, you will notice that a number is shown in the screen of both device. Assuming it shows the number 24, it means that the ground is shaking at 24 gals.

This numbers allows you to actually sound the alarm manually or automatically issue a voice notification (similar to the advance fire alarm system) based on the pre-determined alarm set-point to empower people to choose between life and death situation.

Considering that buildings might collapsed, a "second" of time to react (or take cover for safety) will mean a lot especially when life is at stake.

As shown in the video, people reacted late because of non-notification. It would be tragic if they are in the buildings that collapsed. Thank God that they are not.

With the solution we have, the benefits can be as follows:

• can save more lives
• can be used in mitigation of facilities by shortening the inspection time
• data can be used as a reference data to make sure that the facility is structurally sound
• Utilities such as power can be restored right away
• Airport runways can easily be declared safe at earliest time, etc.

Those are the kinds of benefits that pays that the equipment itself. That without our equipment in the field, the loss of time for non-operation of industrial facilities, schools, offices, Malls, etc. will more.

Going back in time in 1990, a lot of people could have saved their own lives only if we have the same technology that we these days. It's been 23 years, and I believe that people that people are more aware of the dangers.

I do hope that Government agencies have learned the lessons from the past, is currently working to provide better service, so we - the Pilipino people, can have a better future.

Mabuhay ang Pilipino!!!

I used to see this in the TV and street advertisement before - "be honest even if others are not, cannot, will not". I just hope everybody will for the better Philippines.