Installing Broadband Sensors

Introduction:

This manual covers the following tasks related to installing broadband sensors:

Orient sensor Level sensor Connect sensor to DAS (power) Unlock masses (manually or via electronic command, if masses are the type that lock) Center masses (via command) Check waveforms, e.g. stomp test

Note, always handle sensors with care. If you have never worked with sensors or been shown how to install them, you should get help from experienced people, or barring that, carefully read the manufacturer's manual. Never move an unlocked sensor, unless the sensor has no mass locks. Most of the broadband sensors in the EPIC fleet are either Streckeisen STS2's or Guralp 3T's; both models have 3 masses and all 3 need to remain locked during transport.

True North (geographic North) is the convention for orienting sensors in what's known as passive experiments, i.e. generally recording earthquakes, as opposed to controlled sources. You must know the declination angle between true North and magnetic North at the station site and you must know how to properly correct for the declination. If you do not know this, find someone who does; otherwise use magnetic North and make sure you write that on the Installation Sheet. (You will use this information later to construct accurate metadata for the station.)

Fetch the sensor planned for the site and write its serial number on the station's Installation Sheet, preferably in pencil, because if the sensor does not work properly, you will have to try a different one. Loosen the sensor feet (the foot-locking mechanisms may need to be backed off) and shorten the feet (also known as legs) as much as possible. Clean grit off the sensor pad. Place the sensor on the sensor pad and adjust the sensor's position until its orienting keys are precisely aligned.

In the field, you must check:

 

Download Diagram of Vault (jpg)

Construction of the vault for broadband seismometers has a direct impact on data quality. Before construction can begin there are two other important considerations as well; location, and setting. A short discussion of these topics precedes the construction details because you should really pick the right site before going to all the work of building a vault. It takes a long time to find good sites which balance the competing requirements of low noise, access, security, position within the array, power, permission, etc. Finding one site per day is fairly productive.