How does the Raspberry Shake compare to a broadband seismometer?

Seismologists often ask, “How does the Raspberry Shake measure up against a broadband seismometer like the Nanometrics Trillium Compact?”.

The answer: From ~2s to 40 Hz where the frequency response of the Raspberry Shake is flat, the performance is the same. Since automated processing systems like SeisComP3 typically filter from 1-5 Hz, this means a broadband and short-period sensors like the Raspberry Shake are essentially indistinguishable for earthquake detection purposes.

But do not take our word for it, extract some real-life data and see for yourself!

For your enjoyment, we have co-located the following instruments at our PA.BRU2 international seismic station:

  • The reference sensors:
    • A Nanometrics Trillium Compact and Nanometrics Titan paired with an true 24-bit Earthdata 209 digitizer (PA.BRU2..[HH?,HN?])
  • The Raspberry Shakes:
    • A Raspberry Shake RS&BOOM V3 (AM.R9D92.00.[EHZ,HDF])
    • A Raspberry Shake RS4D V6 (AM.R2EFC.00.[EH?,EN?])
    • A Raspberry Shake RS3D V5 (AM.R2417.00.EH?)
    • A Raspberry Shake RS1D V6 (AM.RF248.00.EHZ)

All units are co-located on the same concrete pier and running at 100 sps. All instrumentation was oriented towards North using a gyroscope.

Some background on PA.BRU2

The Raspberry Shake Project owns and operates a Class A seismic vault for real-time earthquake monitoring, sensor development and testing, and experimentation called “BRU2”. BRU2 was finished and brought online in 2011. It houses a Nanometrics Trillium Compact Broadband Seismometer and Nanometrics Titan Accelerometer.

_images/bru2.jpg

Welcome to the jungle! The BRU2 seismic vault and power hut.

Real-time data from BRU2 are available through the IRIS Consortium: BRU2 at IRIS.

Click here for the BRU2 station map. (Zoom out to see the volcano to the East where the Raspberry Shakes are built! And if the map does not load for whatever reason, hit the purple “Update Map” button.)

Instrument Response files

Download the instrument response files in xml format (sc3 inventory-xml in the case of the Raspberry Shakes):

Note

Please note that the latitude and longitude of the Raspberry Shakes has been obfuscated. The real coordinates are: <Latitude>8.794</Latitude>, <Longitude>-82.687798</Longitude>

Continuous waveform data

For real-time streaming and archived continuous data, you can use Swarm to visualize the data in classic helicorder plot mode and then extract the miniSEED data using FDSN Web Services (a quick and easy tool for data extraction):

Example data extraction commands:

$ wget --no-check-certificate "https://service.iris.edu/fdsnws/dataselect/1/query?net=PA&sta=BRU2&cha=HHZ,HHN,HHE,HNZ,HNN,HNE&start=2018-07-22T11:23:00&end=2018-07-22T11:25:00" -O eq20180722a-bru2.ms
$ wget --no-check-certificate "https://fdsnws.raspberryshakedata.com/fdsnws/dataselect/1/query?net=AM&sta=R9D92&loc=00&cha=EHZ&start=2018-07-22T11:23:00&end=2018-07-22T11:25:00" -O eq20180722a-r9d92.ms
$ wget --no-check-certificate "https://fdsnws.raspberryshakedata.com/fdsnws/dataselect/1/query?net=AM&sta=R2EFC&loc=00&cha=EHZ,ENZ,ENN,ENE&start=2018-07-22T11:23:00&end=2018-07-22T11:25:00" -O eq20180722a-r2efc.ms
$ wget --no-check-certificate "https://fdsnws.raspberryshakedata.com/fdsnws/dataselect/1/query?net=AM&sta=R2417&loc=00&cha=EHZ,EHN,EHE&start=2018-07-22T11:23:00&end=2018-07-22T11:25:00" -O eq20180722a-r2417.ms
$ wget --no-check-certificate "https://fdsnws.raspberryshakedata.com/fdsnws/dataselect/1/query?net=AM&sta=RF248&loc=00&cha=EHZ&start=2018-07-22T11:23:00&end=2018-07-22T11:25:00" -O eq20180722a-rf248.ms

Technical Specifications

For full technical specifications including Sleeman plots, see: Technical Specifications.

What is the difference between the RS1D, RS3D and RS4D models?

_images/Comparisons.png

Click to enlarge

*sps = samples per second on all channels

The RS1D, RS3D, RS4D and RS&BOOM have the same capabilities for detecting Earth motion in the vertical dimension. The RS3D replicates these abilities in the horizontal dimensions, providing the user with a fuller view of Earth motion in all 3 dimensions. The difference between the RS1D and the RS4D is that the RS4D has a 3 dimensional accelerometer built into the board. This is interesting for people who live in earthquake zones where the strong motion might be enough to saturate the vertical sensor. With the accelerometer, the Earth motion would remain on scale with the added benefit of being able to detect lateral motion as well.

Some comparisons we did using SQLX

Example 1

It shakes a LOT in Panama and, while writing this manual page on a Sunday a bit before the sun had come up, there was a felt event.

Event details: M3.7, Panama-Costa Rica border region (event ID: rs2018ohriiw). ~10 km North of the BRU2 seismic vault:

_images/rs2018ohriiw.png
Raw data:
_images/sqlx-waveforms-ehz-unfiltered.png

All vertical velocity channels (EHZ, HHZ) unfiltered. Click to enlarge.

_images/sqlx-waveforms-ehz-filtered0.2to10Hz.png

All vertical velocity channels (EHZ, HHZ) filtered from 0.2 to 10 Hz and overlain. No deconvolution/ amplitude correction applied. Click to enlarge.

_images/sqlx-spectra-ehz.png

Spectra of all velocity channels (EHZ, ENZ) unfiltered. Click to enlarge.

_images/sqlx-waveforms-enz-filtered1to10Hz.png

Accelerograph channels ENZ and HNZ filtered from 1 to 10 Hz. Even for this tiny event, the MEMs react nicely. Click to enlarge.

For more details about SQLX visit, sqlx.science. Or email us at sales@raspberryshake.org for a quote.

Closing Comments

We are also often asked, “And when is the Raspberry Shake team going to come out with a Broadband seismograph?”, to which I (Branden) respond, “The Force is strong in the Raspberry Shake development team. Stay tuned for future innovations!”.