SIOSEIS is a computer system for enhancing and manipulating marine seismic reflection and refraction data, sponsored by the National Science Foundation (NSF) and the Scripps Industrial Associates. The system currently runs on SUN, SGI, PC-Linux, PC-CYGWIN, and Mac OSX. X11 and an Unix shell are also required.

SIOSEIS features the use of the geophysical industry standard demultiplexed SEG-Y data format for tape and disk files. Seismic record sections may be produced directly to a raster plotter without creating intermediate files or making additional computer runs. The processing variables are given by the user via free field named parameters and are edited for possible errors before any data are processed. The system was designed for use by people with some training in applied geophysics. Users must know how to use a text editor and use a Unix shell.

SIOSEIS has three features that are particularly useful for processing marine data:

1. Most academic seismic lines are collected over uneven bathymetry. SIOSEIS has the unique ability to define the water bottom, then having a single set of parameters for NMO, mute, decon, etc. reference the water bottom time automatically. This results in an enormous time saving over having to define a new parameter each time there is a major variation in water depth.
2. Marine geophysicists often collect data in very deep water, using a delay to reduce the quantity of data actually recorded. This results in the time of the first data sample being a time other than zero. In SIOSEIS each process that uses time as a variable honors the deep water delay. SIOSEIS processes do not remove the delay by padding with zeroes to force the first time to be zero and adding to the amount of data processed. The use of the deep water delay greatly increases the speed of processing.
3. SIOSEIS has a unique user interface. All user variables are described via free field, order independent, named parameters. The processing order is controlled by a single statement regardless of the order of the processing variables. Very long multichannel lines may be described in full, yet can be processed in small pieces. The program never generates large disk files with processing tables, rather it generates the appropriate information as the data are processed.

SIOSEIS has been under development at Scripps Institution of Oceanography (SIO) since 1978 and has been used by scientists, students, and staff to process multi-channel and one and two channel reflection and refraction data. The system has been used for production processing as well as experimental work with expanding spreads, OBS (ocean bottom seismometers), sonobuoys, ESP (expanding spread profiles), and WAP (wide angle profiles); with sample intervals ranging from 8 milliseconds to .1 milli- second and "unusual" sample rates of 128 samples per second.

The list of seismic processes available is contained in the users' manual.

Some differences between SIOSEIS and some other seismic packages are:

• Use of the deep water delay.
• Allowing the trace length, sample interval, and deep water delay to vary from trace to trace.
• SIOSEIS keeps the data in SEG-Y and does not use an internal data format.
• SIOSEIS runs on all Unix workstations.
• SIOSEIS is issued as a site license, permitting all machines to do seismic processing.
• There are drivers for all raster plotters, thus additional plotting packages are not necessary. SIOSEIS can make "seismic wallpaper" directly.
• SIOSEIS can read SEG-D tape and disk files.
• Most SIOSEIS processes allow time parameters to be "hung" from the water bottom time in the SEG-Y trace header. E.G. processes gain, mute, decon, and nmo reference the water bottom time.
• SIOSEIS has some special techniques for handling refraction data.
• SIOSEIS's geometry is done completely in floating point which allows the subsurface binning to be defined with non-integers.
• Realtime or near realtime processing is possible if the velocity function can be described as a function of water depth.
• SIOSEIS can process data without building any external database files. This allows quick access to any shot.