Whenever there is an earthquake somewhere in the world, our TV screens fill with images of seismic data. Those news report graphics with simplified bite-sized diagrams that inform the masses, but usually get something wrong. Among the images there will invariably be one of a chart recorder drawing a significant earthquake trace on paper, which makes good TV, but is probably miles away from the state of the art in seismology.
We are not seismologists here at Hackaday, so it was extremely interesting to find [Michael D]’s project, Device for Seismic Noise Analysis. In it, he gives a basic primer in seismic sensors, and outlines his take on the subject, a sensitive wideband seismic sensor designed to capture the seismic background noise. It seems that many seismic sensors are designed to capture big events, yet ignore the noise between them from which using suitable software one can glean advance warning of seismic events.
The sensor is a simple design, a ball of significant mass rests upon three piezoelectric microphone elements spaced at 120 degree intervals. An extremely high impedance op-amp circuit converts and integrates the charge from the piezo element to a voltage that can be read by an Arduino Yun which harvests the data. It is a bold claim, but the device is said to have already given advance warning of minor seismic events near its Tennessee test site.
Seismology has featured here a few times before. There was this seismometer using a subwoofer as its sensor, and this project using commercial geophones, just to name a couple of examples.
Nepal | 25 April 2015 | 11:56 NST
It was a typical day for the 27 million residents of Nepal – a small south Asian country nestled between China and India. Men and women went about their usual routine as they would any other day. Children ran about happily on school playgrounds while their parents earned a living in one of the country’s many industries. None of them could foresee the incredible destruction that would soon strike with no warning. The 7.8 magnitude earthquake shook the country at its core. 9,000 people died that day. How many didn’t have to?
History is riddled with earthquakes and their staggering death tolls. Because many are killed by collapsing infrastructure, even a 60 second warning could save many thousands of lives. Why can’t we do this? Or a better question – why aren’t we doing this? Meet [Micheal Doody], a Reproductive Endocrinologist with a doctorate in physical biochemistry. While he doesn’t exactly have the background needed to pioneer a novel approach to predict earthquakes, he’s off to a good start.
He uses piezoelectric pressure sensors at the heart of the device, but they’re far from the most interesting parts. Three steel balls, each weighing four pounds, are suspended from a central vertical post. Magnets are used to balance the balls 120 degrees apart from each other. They exert a lateral force on the piezo sensors, allowing for any movement of the vertical post to be detected. An Arduino and some amplifiers are used to look at the piezo sensors.
The system is not meant to measure actual vibration data. Instead it looks at the noise floor and uses statistical analysis to see any changes in the background noise. Network several of these sensors along a fault line, and you have yourself a low cost system that could see an earthquake coming, potentially saving thousands of lives.
[Michael] has a TON of data on his project page. Though he’s obviously very skilled, he is not an EE or software guy. He could use some help with the signal analysis and other parts. If you would like to lend a hand and help make this world a better place, please get in touch with him.
Continue reading “We Have A Problem: Earthquake Prediction”
[10DotMatrix] has a budding interest in seismology, so she decided to make her own seismometer out of some easy-to-find materials. Seismometers are prohibitively expensive for hobbyists, but thankfully it’s really easy to build a usable siesmometer out of simple parts. [10DotMatrix]’s seismometer is built around a modified subwoofer, which acts as a transducer for the earth’s vibrations.
The subwoofer is mounted to the bottom of a tripod, which forms the structure of the seismometer. A slinky is stretched between the top of the tripod and a weight that rests on the coil of the subwoofer. Whenever the ground shakes, the slinky and weight vibrate and induce current in the voice coil.
Since these vibrations are usually quite small, the output of the subwoofer needs a bit of amplification. [10DotMatrix] fed the output of the woofer to an AD620 op amp, which amplifies the signal to a measurable level. The amplifier’s output is fed into an Intel Edison board, which samples the voltage and transmits it to a web dashboard for online viewing.
If you’re shaking with excitement about seismic measurements you’ll surely be interested in this similar method which uses a piezo element as the detector.
Chart recorders are vintage devices that were used to plot analog values on paper. They’re similar to old seismometers which plot seismic waves from earthquakes. The device has a heated pen which moves across a piece of thermally sensitive paper. This paper is fed through the machine at a specified rate, which gives two dimensions of plotting.
[Marv] ended up getting a couple of discontinued chart recorders and figured out the interface. Five parallel signals control the feed rate of the paper, and an analog voltage controls the pen location. The next logical step was to hook up an Arduino to control the plotter.
However, once the device could plot analog values, [Marv] quickly looked for a new challenge. He wanted to write characters and bitmaps using the device, but this would require non-continuous lines. By adding a solenoid to lift the pen, he built a chart recorder printer.
After the break, check out a video of the chart recorder doing something it was never intended to do. If you happen to have one of these chart recorders, [Marv] included all of the code in his writeup to help you build your own.
Continue reading “Printing Text With A Chart Recorder”
Well, if you hadn’t noticed the news there has been a little bit of a shakeup on the east coast. I just arrived home after being evacuated due to a 30 second rumble the likes of which has not been felt on the east coast in something like 114 years. In lieu of the not so devastating but earth shaking event we thought we’d put together a few earthquake related links for you.
Earthquake-proof Wine Rack
First off instructables user [jofish] has a quick remedy if earthquakes are constantly destroying all the wine on your wine rack. He researched some existing commercial products and simply copied them by stapling cheap O rings to the front of the rack. We assume the back of the wine rack is secured to the wall as well.
Next up is a vertical seismometer from [Mike] over at mikesense.com. This was in response to a slightly more threatening 7.2 earthquake he experienced in Baja California last year. A vertical seismometer measures the movement of a weight either electronically or mechanically, and then damps the motion of the oscillation by a magnet or some other means. This particular design is known as the AS-1 developed by [Jeff Batten]. Matt’s page has links to everything you’d need to know including build videos.
Predict Seismic Activity with Hard Drives
If you are looking for some non-conventional ways of tracking seismic activity we have a pair of articles that detail earthquake tracking using your disk drive’s accelerometer. [Michael Stadler] realized the potential for all these sensors and released a program that creates a peer-to-peer network compiling data from the sensors. We are not too comfortable with the prospect of somebody tracking every time we drop or kick (or drop-kick) our laptops but 2500 users in Asia downloaded the software in ’06. The second article details an effort lead by IBM to monitor the fixed hard drives in server racks which generally remain far more stationary.
Simple DIY Earthquake Simulator
Finally for those of you who want to cause (miniature) earthquakes, we dug up this MTU project using plywood, an electric drill, rubber bands and some bearings to fabricate a DIY shake table (PDF warning). We are sure there are tons of improvements that can be made but this is a pretty fun project if you have a bunch of CNC parts lying around (we wish we did).