See also: the Google Group where you can easily search the archives for questions similar to your own.
Question: The Shake box seems to come with some nice trim screws to set it level. How though is the unit meant to be coupled to the ground/concrete/slab/table...? The last few earthquakes I’ve experienced here in New Zealand would of sent the Raspberry Shake bouncing off the table or sliding over floor which means it will not actually be recording what it is meant to? How is it proposed to couple it to the horizontal surface?
Answer: Shake does not need to be “anchored”.
Raspberry Shake is a weak motion device, like most seismometers are. It is designed to measure sub-micron movements. It probably completely clips between 0.1 and 0.2 g.
If during an earthquake objects are in the air then surely 1 g has been exceeded. Just yesterday I was watching youTube videos of the last New Zealand earthquake and yes things were moving. Shake and any other seismometer would be totally saturated and the data would be useless even if they were anchored.
Seismologists use accelerometers which have a range above 1 g commonly set to 2 g and can be set to 4 g. These devices are anchored. In a Class A seismic installation you would have a seismometer, and accelerometer that goes to DC and a GPS. This would allow for the huge dynamic range that you will get in a large earthquake. The accelerometer to DC and the GPS would allow you to see the displacements that a velocity sensor like the Shake will not show.
Answer: This is a good question and one that is tossed around here at OSOP. Geophones are made by lots of companies and in lots of natural frequencies and cases and coil types. We think that the geophone used in Raspberry shake will have over 95% of it output out to about three degrees. A quick and dirty test of the undamped output of the Raspberry Shake’s 4.5 Hz geophone was performed. We did the test at 10 Hz to get away from the amplification of the resonant frequency. We moved the geophone 1 mm. 1mm at 10Hz is strong shaking. From 0 to 3 degrees of tilt we could not see any significant difference in the output. It was not until 6 degrees that we could see a change and not until 15 degrees that the output was meaningless.
We can definitely say that if the bubble is mostly within the little circle on the level built into the acrylic box, that things are ok. From the test we have done, I think that the bubble level we provide will achieve the +/- .5 Degrees as long as the bubble is centered in the circle.
Later, one of our backers, Brett, responded: “I did a quick test to check the bubble sensitivity. It took about one turn of the leg screw located on the center line to move the bubble from centered to be solidly touching the black ring. That’s 0.8mm over 123.5mm, the perpendicular distance from that screw to a line between the other two legs. That ratio is 0.00648 and taking the ArcSin = 0.37 deg. of tilt, which is slightly better than you suggest. Probably the biggest factor will be how well the geophone guts are aligned with the bubble level. Super leveling is not going to be an issue.“
Question: Might accelerometers be on your road map?
Answer: Making an accelerometer version of Shake would not be hard, we have some. The problem is that under normal conditions the output looks like a flat line and it is very very boring. Small (< Magnitude 3 earthquakes) are buried in the noise. Like watching grass grow. It is not even useful for normal locating and monitoring seismology, it is only useful for making intensity maps for strong earthquakes.
On the other the hand Raspberry Shake is exquisitely sensitive and you will see everything around you, too much sometimes. You will see all of the local and regional earthquakes.
Once we get the shipping done we will turn our attention to working the kinks out of the software and writing the book on how to interpret what you record. We are all excited about this project.
The schematic for Shake is not available. Much of the software is open. Our reason for not making the schematic available is that if we made the hardware open and the firmware that went with it, we would see Raspberry Shake on Alibaba before the Kickstarter campaign was even over.
We align ourselves in many ways with the folks at Pololu when they make this statement about open hardware: See article here. Pololu put a huge amount of work in writing that piece, long but worth the read.
Additional note: All Raspberry Shakes purchased during the Kickstarter campaign are exempt from the license requirement.
We do not recommend updating the Raspberry Pi’s OS The problem with updating the OS, without regard to the operating environment it supports, is that the possibility exists for the update to break some instance of infrastructure on which the executing system relies. It is possible that the Raspberry Shake unit will simply stop functioning and you won’t know why. Rather, it is preferred that the maintainer of the system fully understand the implications of any OS update on the system itself before allowing such an update to take place. Only once an OS update has been fully vetted (vs. all activities it is required to support) should it then be rolled out to individual units in the field. For more details see: Ready, Set, Get Hacked! Security and Raspberry Shake.
Please send an email to the Google Group list with the subject: “Bug Report: <some summary message here>”