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General Information

Data Type

3D Multichannel Seismic

Data Acquisition System

Boomer and P-cable system

Contributor

Pacific Gas and Electric Company

Dates

Started on Aug. 22, 2012, and ended on Oct. 5, 2012.

Description

Reprocessed 3D seismic-reflection data and neural-network fault cube of field activity P-04-11-CC, offshore Point Sal, central California, 2012-08-12 to 2012-10-05.

Purpose

This data release includes boomer 3D seismic data collected in 2012 offshore Point Sal, central California as part of PG&E’s Central California Seismic Imaging Project (Pacific Gas and Electric Company [PG&E],2014). The U.S. Geological Survey conducted advanced post-processing and neural-network fault calculations on the data for improved fault detection (Kluesner and Brothers, 2016).

Following generation of the cleaned, 3D, volume- and neural-network fault cube, each volume was exported using the OpendTect software package. Both the cleaned 3D volume and fault volume are in SEG-Y format and are provided here.

Any use of trade, product, or firm names are for descriptive purposes only and does not imply endorsement by the U.S. Government.

Notes

Suggested Citation:

Kluesner, J. W., Brothers, D. S., and Sliter, R. W., 2017, Reprocessed 3D seismic-reflection data and neural-network fault cube of field activity P-04-11-CC, offshore Point Sal, central California, 2012-08-12 to 2012-10-05: U.S. Geological Survey data release, doi:10.5066/F7HD7TKM

Geographic Features

Central California, Point Sal

Dataset Information

Processed Methods

Seismic Reflection

Processed Data Classes

3D Migration

Data File Formats

SEG-Y

Embedded Navigation

Yes

Data Class

Processed

Seismic Data Provenances

Digitally Acquired Digital SEG

Data Media

Online

Notes

To download full dataset click on "Download". To download individual files click on "View Contents"

Processing

Seismic data were acquired using a triple-plate boomer source operated at 1.75 kJ and the P-Cable streamer system. The 3D data show a frequency range of approximately 100-700 Hz, with a dominant frequency of 200-225 Hz (PG&E, 2014). The P-Cable system consisted of 14, 8-channel digital streamers with 6.25 m hydrophone group spacing (Nishenko and others, 2012; Ebuna and others, 2013). Data were sampled at 0.25 ms with a record length of 0.75 s two-way travel-time. Seismic processing steps conducted by Fugro Consultants included quality control, tidal corrections, velocity analysis, NMO correction, stacking, surface related multiple elimination, deconvolution, crossline statics, and pre-stack migration (Fugro Consultants Inc., 2012; PG&E, 2014). However, upon public release and inspection by the USGS, significant high-frequency noise was observed, limiting the interpretation of imaged fault structures (Kluesner and Brothers, 2016).

The publically released 3D seismic data were downloaded and analyzed by the USGS and a post-stack data-conditioning workflow was designed to reduce noise, short-period multiples, and enhance the overall quality. The workflow followed the methods described in Kluesner and Brothers, 2016. Data were imported into the OpendTect software package, and a dip-steering volume was calculated using a 1x1x1 (inline, crossline, sample interval) calculation window. Following dip-steering calculation a median filter was applied with a 1x1x1 step-out, resulting in a smoothed 3D volume of dip and azimuth information for all seismic events. The dip-steered median filter was then applied to the data with a 1x1 (inline, crossline) stepout, with no time window. Filtered results were then subtracted from the original data to produce a volume with significant noise suppression. Both random and apparent acquisition noise were suppressed, while enhancing laterally continuous events.

Following filtering and noise suppression, a post-stack 3D predictive deconvolution filter was designed in order to suppress apparent ringing within the data. Throughout the 3D volume, the seafloor reflection suffers from a long wavelength, masking geology below. The filter effectively suppressed the ringing/short-period multiples and also sharpened reflections at depth.

For enhanced fault detection, a neural-network multi-attribute workflow was designed that used 32 different seismic attributes. The 32 attributes, which consisted of calculations such as similarity, curvature, and noise, were used as input nodes in the neural-network. The hidden layer of the neural-network consisted of 16 nodes, and user picks of faults and non-faults were used to supervise the network training. Training was stopped when the normalized root-mean-square (RMS) error reached a minimum value (less than 0.5), along with misclassification percentage of picks. Post training, a 3D volume was generated (fault cube) that contains fault probability measurements scaled between 0 (non-fault) and 1 (fault). This information was then projected onto vertical and horizontal seismic slices to help identify and interpret probable faults imaged within the dataset.

Navigation Information

Datum

World Geodetic System 1984 (WGS84)

Related Publications

Ebuna, D. R., T. J. Mitchell, P. J. Hogan, S. Nishenko, and H. G. Greene, 2013, High-resolution offshore 3D seismic geophysical studies of infrastructure geohazards: 26th Symposium on the Application of Geophysics to Engineering and Environmental Problems, 311-320, http://www.proceedings.com/18180.html.

Fugro Consultants Inc., 2012, Software validation of Uniseis and 3D data qualification of 2010 - 2011 high-resolution marine survey data, Offshore Diablo Canyon Power Plant, Central Coastal California Seismic Imaging Project: Fugro Consultants Inc., No. PGEQ-PR-03 (Rev0), FSI Project No. 2011-4493, 1-67.

Kluesner, J. W., and Brothers, D., 2016, Seismic attribute detection of faults and fluid pathways within an active strike-slip chear zone: New Insights from high-resolution 3D P-Cable seismic data along the Hosgri Fault, offshore California: AAPG/SEG Interpretation, 4, 1, doi: 10.1190/INT-2015-0143.1.

Nishenko, S., P. Hogan, and R. Kvitek, 2012, Seafloor mapping for earthquake, tsunami hazard assessments: Sea Technology, 53, 15-20.

Pacific Gas and Electric Company (PG&E), 2014, Offshore low-energy seismic reflection studies in Estero Bay, San Luis Obispo Bay, and Point Sal Areas: PG&E Technical Report, GEO.DCPP.TR.14.02, http://www.pge.com/includes/docs/pdfs/safety/systemworks/dcpp/report/Ch3.GEO.DCPP.TR.14.02_R0_txt.w.ITR.pdf.

Location

Area covered:   18 square kilometers

Acquisition Parameters

Name Value
Field Activity Identifiers P-04-11-CC
Horizontal Datum World Geodetic System 1984