Earth Science & Seismology
Live Helicorder from Delta Community College - 5 minute updates
Click on image below for all Delta helicorders
Important Observation Notes about Seismograms
The image above depicts a live seismogram as recorded by a sensor approximately 5 miles ENE of the Delta facilities. An actual sensor will be set up at Delta by the Spring of 2005. The seismogram above is unfiltered. Unfiltered means that normal foot traffic, road traffic, lightning discharges, strong wind, and the occasional passing train will register on the images. With training, one can be able to identify the different signatures. Processed images of events on the main page are filtered so that the abovementioned phenomena will not be shown. Small earthquakes will not likely show up on the live seismograms as they are frequently embedded in the background noise and must be filtered.
|This is an example of either foot traffic or a passing vehicle. Note the spikes are temporary and only last for a few seconds. Shown here are two spikes side by side.|
The above image is a distant quake from near the island of Sumatra. Notice the length is much longer than that of the traffic above.
The above image is a regional 5.6 event near Baja California.
The above image is the passage of a nearby train. It will likely only show up on the vertical channel.
Channel 1 or Sensor 1 is a "Mini-Lehman" type sensor which is oriented E/W and has a period of 16 seconds. This is one of my favorite instruments in that it does an excellent job picking up both local and distant events and minimizes foot traffic in my home. It also picks up a nearby train which cannot be fully filtered out.
Channel 2 or Sensor 2 is a large "T-Max Lehman" type sensor constructed by John Cole of Houston, Texas. It is oriented on an E/W axis and has a resonance period of approximately 26 seconds. It is very sensitive in picking up many events both local and distant; however, it is also very sensitive to foot traffic in my home.
Channel 3 or Sensor 3 is a vertical sensor. It does an excellent job in detecting short period events highlighting "P" waves in earthquakes and all local events. Unfortunately, its location is near a railroad track which is the same period as the sensor. Therefore, major interference of passing trains often occurs with this sensor. Otherwise, it does a great job in picking up local events and larger distant events.
Latest Earthquake Advisories
Tsunami Information Bulletin
Tsunami Watches and/or Warnings
Delta Live Webicorder Display
PNSN Webicorder Displays - Pacific Northwest
Live seismograms and explanations of how to read the trace