Maryland Department of Natural Resources

Seismic Network Components


The seismic network consists of a remote sensing station, equipment to transmit and receive data, a computer to log and display the data and an Internet connection to distribute the data. Signals from the seismometer are sent via a transmitter at Soldiers Delight to a receiver on the roof of the MGS building. From the rooftop receiver, the data signal is sent to a dedicated computer for processing, display and storage. The data is then made available on the Internet from our World Wide Web site.

Seismic network data path


Data Collection and Processing

The Maryland Seismic Network uses a variety of software to collect, analyze and display data. Some of this software was developed by MGS, and some came from other sources.  Earth movements are detected by the seismometer and converted to a digital signal by the instrument's internal digitizer. The digitizer also compresses the data before it is transmitted to the Survey laboratories. The digitizer uses internal, proprietary software for these tasks. When the digital signal arrives at the Survey it is decompressed and made available to our network by SCREAM! software. This software is available from Guralp Systems

The raw data output by SCREAM! is processed by Earthworm software, available from USGS Earthworm Development Group. Earthworm provides several services for seismic data processing. One of the primary functions of Earthworm is to store seismic data from SCREAM!. Earthworm stores the data in a large file on a hard drive disk. Because the data is constantly being transmitted and stored, and there is a finite amount of disk space for storage, only a certain amount of data can be stored. Therefore, the most recent data received is stored and data older than some chosen date is discarded from the disk file. This kind of data storage file is called a circular buffer. The circular buffer for Earthworm data is refereed to as the wave ring. Thus the primary function of Earthworm is to create and maintain a wave ring.Earthworm also imports seismic data from other institutions into our wave ring. Any data in the wave ring is available for distribution, analysis and display.

MGS exports wave ring data to the Lamont-Doherty cooperative seismic network for analysis.