Create a node-red-contrib-openeew package and STA/LTA node

[andygrillo]

Currently we are using a peak acceleration value to declare an earthquake. However any acceleration can trigger this (cars, people, drilling).

Short term average/long term average (STA/LTA) is well used in seismology to detect earthquakes. For OpenEEW this would work by comparing a small window of 1 second of data against a larger window of 10 seconds of data. The STA/LTA output value is then compared against a trigger threshold.

An example of this in python is here: https://github.com/openeew/openeew-detection/blob/master/openeew/detection.py

[johnwalicki]

Tasks:

• Convert the algorithm (currently written in Python) to a javascript function
• Test the javascript function in a Node-RED Function node
• Review the function with the seismologist experts
• Create a node-red-contrib-openeew node that runs the algorithm on message input
• Host the npm package in this OpenEEW github (as a separate repo directory)