A NOTE ON TIME
Please note that all seismic files are recorded in Universal Coordinated Time (UTC), which is similar to Greenwich Mean Time (GMT). This is a convention for all seismic stations in the world. UTC is five hours ahead of Eastern Standard Time and four hours ahead of Eastern Daylight Time. Each Ohio Seismic Network station uses a GPS receiver for precise time. A conservative software program indicates if an hourly seismogram file has at least 0.1-second time accuracy by a stamped notation of "Time Lock=Yes" at the bottom of the displayed seismogram or a "Time Lock=1" line in the raw data file. Conversely, a "Time Lock=No" or "Time Lock=0" message indicates that the software could not ensure 0.1-second accuracy for that particular hourly file.
REQUIRMENTS FOR VIEWING SEISMOGRAM
Ohio Seismic Network seismograms are most easily, and best, viewed on a Macintosh computer with OS 8 or OS 9 using the SeismoView software developed by Dr. Larry J. Ruff (SeismoView is not OS X compliant at this time). SeismoView allows both horizontal and vertical manipulation of the seismogram, a filter that removes microseism noise, and a feature to pick phase arrivals and wave amplitudes/periods. To get a free copy of SeismoView 2001.5 click here to download. A tutorial on downloading and viewing seismograms is available here.
At the current time, a PC-compatible program comparable to SeismoView is not available. However, the AH ASCII format seismograms can be downloaded and imported into Windows spreadsheet programs for viewing.
DOWNLOADING AND VIEWING OHIOSEIS SEISMOGRAMS
- Click on the desired OhioSeis station from the Station Book link on the Ohio Seismic Network Page.
- Click on the Directory of Seismograms
- Click on the desired day
- Click and hold on the desired hour. A drop-down menu will appear and, while still holding down on the mouse button, go to "Download link to disk" (Internet Explorer) or "Save Link As" (Netscape 4.7) and release (Netscape 6.0 Click on the desired hour and a dialog box will appear asking if the file should be saved, click "Save File" button).
- Click Save in the desktop window
- Open SeismoView
- Click File in upper left of top bar, then click Open SeismoGram file in drop-down menu
- Highlight desired file in Desktop window
- Click Open in desktop window
- Click Window on top bar, then click Seismograms in drop-down menu
- Go to Plot Control on top bar, click and set PlotControl (i.e. 1-128), then go to Time axis and set (i.e. 1, 4, 10) to manipulate the seismogram. Use the horizontal scroll bar to look at each minute or part of the seismogram.
- The Analysis feature of SeismoView permits filtering of long-period noise, picking of phase arrivals, and determining wave period and amplitude for magnitude calculations.