Introduction

The SpRIT package is designed to be used with rapid, portable deployments of single, three-component seismometers. It has been tested extensively and designed in part to work with the low-cost Raspberry Shake 3D (RS3D or RS) seismometers. However, it can theoretically be used with any seismometer for which the instrument sensitivity is known and which produces output that can be read by the Obspy python package.

Equipment

Equipment needed ( required)*

• *Seismometer
• *Power source and/or converter (may differ depending on seismometer
• *GPS receiver (for location)
• *Notes (recommended to use template), including pen or pencil
• Shovel
• Bucket or other wind shield (to protect from wind/elements)

Additionally for the Raspberry Shake:

• *USB GPS antenna (and USB converter)
• *Hotspot/ethernet: to shut instrument down at the end of each site
  • Tablet/phone/computer: with hotspot, anything with wifi/browser can work; with ethernet, need a PC with ethernet output or USB adapter
• *Time-keeping device, accurate within 1 min of UTC (phone, tablet, computer, GPS, smartwatch)

Site Selection and Approach

• Locate site (either from map or based on data needs)
• Check surroundings to ensure site is safe. If it is not, do not collect data
• Park vehicle far enough from actual site (25-50 feet is usually sufficient) so excessive noise is not introduced when you move it during acquisition.
• Select site (including side of road, if relevant), depending on things like infrastructure, soil type, safety, etc
• Locating your site with reference to something easily apparent from aerial imagery (and noting that in the field notes) can help when geolocating your site later (example: directly across the street from large driveway)

Data acquisition

After you have assessed and chosen the site, take the following steps:

In short (details for each step are below):

• Select Site
• Clear Site (i.e, take a shovel and remove grass, etc. to make a small patch of bare ground on which to put the instrument)
• Connect cables to the Raspberry Shake:
  • Set the Raspberry Shake into the ground
  • Put on the bucket and run the cables out so the bucket is not resting on them
• Record site location using GPS coordinates
• NOTE THE START TIME! (24 hour time is best: 15:00, not 3:00 PM)
• Plug in/connect the battery to power on the Shake
• Walk away gently
• Wait (at least) 20 minutes
• NOTE THE END TIME! (24 hour time is best: 15:00, not 3:00 PM)
• End recording/Shut down Shake
• Disconnect/unplug the battery
• Disconnect the other cables and collect equipment as needed

Detailed Acquisition steps

1. Site selection (see above)
2. Clear Site
   • Clear area where Shake will be of grass and other obstacles with shovel (you can also dig slightly if necessary, especially on windy days). Usually, this leaves an area of bare dirt about 1’x1’ or a little smaller.

For Raspberry Shake

3. Connect cables to the Raspberry Shake:

   • Connect the GPS to the USB port on the outside of the Shake enclosure
   • Connect the power cable to the port on the outside of the Shake enclosure (DO NOT CONNECT THE POWER CABLE TO THE BATTERY YET!)

4. Set the seismometer into the ground

   • Slowly push the legs into the ground while watching the bubble level and making slight adjustments to ensure it is straight.
   • The bubble levels on the seismometers are often quite sensitive, it does not need to exactly in the middle of the circle. A goal should be that the bubble is at least not against the side.
   • It is better to be slightly off-level than to make adjustments after the legs are all the way in. If it is too far off, take it out and start over.

5. Put on the bucket and run the cables out so the bucket is not resting on them

6. Record site location using GPS coordinates

7. Adjust parameters on the instrument as needed

8. NOTE THE START TIME OR DURATION! (24 hour time is best: 15:00, not 3:00 PM)

   • FOR RS: START TIME is the MOST import parameter you will record in the field.
     • If your time reads 14:34, remember that this can be anywhere from 14:34:00 - 14:34:59. So that we do not cut off any data unintentionally, it is better to lose a minute of data during processing than have extra time noted as part of the record where we were not actually recording anything. So, in the notes, record either 14:35 (or 14:36 if you want to be extra safe) as the starting time.
   • FOR OTHER INSTRUMENTS: duration of acquisition may be determined beforehand. In this case, put this in your notes.

9. Turn on the instrument acquisition

   • FOR RS If battery is separate, plug in/connect the battery to power on the shake (see Powering on the Raspberry Shake section below for more information)
   • Two options for battery placement:
     • On top of the bucket to ensure it does not blow over
     • As far away from the seismometer as reasonable (to give the Shake space)
   • FOR TROMINO: Navigate to the Initial Menu > ACQUISITION > ACQUIRE menu
     • “TROMINO TRACES” will appear on the screen, followed by a chart showing the data/traces for the three components after a second or two

10. Walk away gently (so as not to introduce unnecessary noise)

11. Wait (at least) 20 minutes.

    • 30-45 minutes is preferred particularly where bedrock is expected to be relatively deep. (Low frequencies require more time to resolve).
    • Usually 20 minutes is sufficient for data analysis, but sometimes a longer duration may be useful, especially if there is a lot of noise that will likely need to be remove later
    • We may also end up removing a few minutes on either side of the recording to ensure we are only using good and real data, so extra time can be useful for that reason too.

12. NOTE THE END TIME! (24 hour time is best: 15:00, not 3:00 PM)

    • Just as with the start time, it is ok to adjust the time by a minute (or two) to ensure we are only using real and good data.
      • In this case, if your time reads 14:58, it is ok to mark 14:58 as the end time since the earliest the time could be would be 14:58
      • You can also do 14:57 or 14:56 if you feel that you introduced unusable noise while you were approaching/close to the site

13. End recording/Shut Down seismometer FOR RS * Connect via hotspot (or ethernet if needed) to Shake * Go to https://rs.local/ * If this does not work, you may need to figure out the Shake’s IP address. * Fing may be used for this. * Then, type the IP address into the browser. * Click the hammer icon (Actions) next to the station name. * Click the Actions menu * Click the Shut Down button * You should receive a notification indicating that the Raspberry Shake has been shut down

14. Disconnect/unplug the power source

    • For RS It is recommended that you do this on the battery side, not on the enclosure side, since the enclosure side must be unscrewed and can turn on again briefly/accidentally during the unscrewing process

15. Disconnect the other cables and collect equipment as needed

Instrument-specific notes:

Raspberry Shake

Powering on the Raspberry Shake

The Raspberry Shake records one file per day. More on this later (see the Downloading Data section). Because of this, it immediately needs to figure out what the date/time is when it is powered on. This is done either by internet connection or through GPS. Since we likely do not have internet in the field, IF THE GPS IS NOT CONNECTED THE TIME WILL BE WRONG. This is especially important since time is the only way to know which data is associated with which site. If the time is not updated (via GPS, for example), it will simply assume it is the same time as the last time it was turned off and will continue counting from there.

When the Raspberry Shake is powered on, it automatically and immediately (within a couple seconds) begins recording data. It does take a minute or so for the components to “warm up” but we can either get rid of this data, or–usually what we do–just correct for this by de-trending the data.