_REVISION - C1996083 ‎(2)‎

• Permit No: C1996083
• IBM Index Class Name: REVISION
• Doc Name: Seismic Event Data Acquistition and Processing Distribition and Coordination Across PC-Based Network
• Type & Sequence: PR10
• Media Type: D
• Archive: No

with battery storage. Seismic data are transferred to data processing workstations on the network
via 2.4-GHz,direct-sequence,spread-spectrum wireless transceivers.
While the PC-104 computers can operate the four- and eight-channel A/D boards under
Windows95/98/NT, DOS, and Linux, Linux was selected as the operating system of choice
because laboratory tests showed that it allows the fastest error-free sampling rates. Samba, an
open-source file system server, was used to give Microsoft Windows-based network nodes access
to files on the Linux PC-104 units. The 486-100 MHz PC-104 computers are placed at the point of
signal digitizing to alleviate a data transmission bottleneck encountered in some applications of
method 2.
In method 2, seismic data are continuously sampled and transmitted back to a centralized
processing computer on the network, where they are examined for discrete seismic "events."The
number of channels that can be recorded at the high sampling rates is limited by the available
bandwidth of the spread-spectrum radio network. Adding additional channels reduces the
maximum possible sampling rate. To increase the number of stations providing data via radio link
without reducing the sampling rates, the distributed PC-104 approach was developed.
Continuously sampled seismic data are examined by the embedded processor and discarded, if so
desired, when trigger conditions are not met. Data files meeting the trigger criterion are locally
saved to disk and/or pulled off the remote node with the wireless network connection. Providing
the task load is not too great on the remote computer, additional processing may also be done.
Work is currently underway to use the networked PC-104 platforms with inexpensive single-
frequency Global Positioning System (GPS) receivers for continuous measurements of subsidence
and other factors of importance in mine safety studies(Swanson et al.,2001).
Time Base Synchronization
Each data acquisition system records a common timing signal derived from GPS satellites.
Underground data acquisition systems receive these time codes via copper or fiber cables. During
the initial part of the data processing cycle, the timing signals are decoded and the time base of
each seismic record is adjusted.
SOFTWARE
Networking
Several different types of networking and operating system software were examined during
system development. As the initial data acquisition systems were restricted to DOS, peer-to-peer
networking to the data processing platforms was achieved using the NetBEUI protocol available in
Workgroups Add-On for DOS.TCP/IP protocol is used to connect to Linuy�based data acquisition
PC's.The main seismic data processing PC's use either Windows9x or NT operating systems.
Use of mining companies' general-purpose LAN's for seismic data acquisition and processing
has met with mixed success.If there is no one on site to tend to the monitoring system on a regular
basis, a stand-alone, or isolated, LAN is preferred. This avoids problems associated with many
diverse users, corporate firewalls, and other security issues. If the corporate system administrator
is on site and attuned to the needs of the seismic monitoring system,problems can be minimized.
By isolating the data acquisition nodes onto a separate LAN,these problems can be largely limited
to periodic temporary disruption of the automated data processing.