The `BKNAS' Seismic Data Format Version 1.0 ------------------------------------------- Note: This note summarizes information previously given in AG Notes 304 and 359. 1. Introduction and a Little History Seismic data edited at Blacknest were originally written to magnetic tape as IBM format `master tape' files. The format of the data contained in these files varied, due to the separate handling of analogue, digital, broad band, long period and short period array data over the years, but the data were always written in binary form. The files had six standard 80 character labels: four tape headers (VOL, HDR1, HDR2, and a user label), and two trailers (EOF1 and EOF2). The information contained in these labels was the only concurrent information available regarding the seismic data contained in the file. A short description of each of these data formats is given in section 4. A new data format was developed for the Digital MicroVax at Blacknest in the early 1990's. This was the Blacknest raw data format (BKNRW), again, a binary data format but allowing for a 32000 byte header to contain array information and so on. The format is described in section 3. The Blacknest ASCII format (BKNAS) has since been created to allow for easy transfer of data between different operating systems at Blacknest and elsewhere. IMPORTANT POINT: --------------- The BKNAS format is essentially a super-format, able to describe all the other edited data formats which have been used at Blacknest to create master tape files. --------------- In the BKNAS format, the multiplexed seismic data are displayed in ascii, readable columns, one line per time sample. Version 2.0 of the BKNAS format was developed to allow external users access to data contained in the seismic data archive (`robby') at Blacknest via an automatic data request manager (AutoDRM). It contains a different header format which excludes all local parameters. The format of the seismic data is the same as in version 1.0. For more information on this format, consult the Blacknest AutoDRM documentation. Version 3.0 of the BKNAS format is currently being developed for the new in-house digitizer. A description of the new format will be available when the new system is implemented. 2. The BKNAS Data Format 2.0 Elements of the format The BKNAS data format is an ascii format and has three basic structures: 1. One 80 character `File' card; always present. 2. Header cards, either: i. Three optional 80 character tape header cards, comprising: 1. HDR1 card, copied directly from the master tape header 2. HDR2 card, copied directly from the master tape header 3. User label, an almost direct copy of the master tape header The three tape header cards are only present in files which do not have the full 400 line `BKNAS' header. For information on the data formats which use these header cards, see section 4. or: ii. Optional 400 line, 80 characters per line `BKNAS' header. For information on the `BKNAS' header, see section 3. 3. Lines of data: one line per time sample, one column per channel 2.1 The File card The File card format: Columns Format Description -------------------------------------------------------------- 1-5 A5 Always 'BKNAS', the format type 7-10 F4.1 Version number of the format, currently 1.0 12-16 A5 Full station code name as known in-house 18-19 I2 Number of channels (thus columns) of data 21-23 I3 Number of lines of header following this one. This is normally 3, except for old BKNRW format input data, where it is 400 25-27 I3 Number of non-waveform data samples per channel (and thus the number of lines of such data) immediately following the last line of header 29-35 I7 Total number of samples per channel contained in this file, whether waveform data or not. Thus this field equates to the total number of lines of data in the file following the last line of header. 2.2 The tape header cards These cards are only present for those files which were originally non-BKNRW format master tape files. 2.2.1 The HDR1 card (80 characters) The HDR1 card format: Columns Format Description --------------------------------------------------------------- 1-4 A4 Always 'HDR1' 5-16 A12 Origin of the data, either: 'BKNSTDATCENT' for internal use at Blacknest 'BSSPAA.BNST.' for use elsewhere 17-21 A5 (Original) data type, for instance 'BKNRW', 'SDAT', 'AD21', 'WBA'. This field may not necessarily match that in the user label. Use the user label data type in preference. See section 4 for more information. 22-27 A6 Original number of the master tape on which the file resides 32-35 A4 Original file number on master tape 43-44 I2 Last two digits of the year when the original tape file was created 45-47 I3 Day number of the year when the original tape file was created 61-80 A20 Comments (rarely used) 2.2.2 The HDR2 card (80 characters) The HDR2 card format: Columns Format Description --------------------------------------------------------------- 1-4 A4 Always 'HDR2' 6-10 I5 Number of bytes in each data record, e.g. 4012 for SDAT data, 4200 for AD21. 18-80 A63 Comments (rarely used) 2.2.3 The User Label (80 characters) The user label format: Columns Format Description --------------------------------------------------------------- 1-11 A11 Date of the event, in the form 'DD-MMM-YYYY' 13-20 A8 Time of the event, in the form 'HH:MM:SS' 22-73 A52 Comment. The information here has no fixed format, although it is often as follows: cols 22-63: Epicentre and processing data cols 64-66: Event backbearing (I3) cols 68-71: Event speed (F4.1) 74-74 A1 One character station code, which should match the full station code given in the file card and also the station code given in the data 76-80 A5 (Original) data type, for instance 'BKNRW', 'SDAT', 'AD21', 'WBA'. This field may not necessarily match that in the HDR1 card. The field here should be used in preference. 2.3 The `BKNAS' format header See section 3. 2.4 The seismic data The seismic data format, one line per time sample, is as follows: Columns Format Description --------------------------------------------------------------- 1-1 A1 *One character station code, which should match the full station code given in the file card and also the station code given in the user label. 2-11 A10 *Date and time of the data sample, in the form 'YDDDHHMMSS', where 'Y' is the year of decade 12-on I6 data samples, one per channel. is the number of channels in the data, given in the file card. * These fields are only present at the start of each original data block, and where the information exists in the original format (SDAT, DSASP, BSASP, SDLP, ADC4 and WBA, but not BKNRW, AD21, BAPPL, ADC1 or ADC2). Where the information is not present, the first eleven columns are left blank. 3. The BKNAS Header Format The BKNAS format is the Blacknest raw, edited data format. A maximum of 32 channels can be written into one file. The header consists of 400 by 80 character lines, a total of 32000 bytes in all. IMPORTANT POINT --------------- The line containing the BKNAS information is NOT part of this header. However, some of the information is repeated in the header for use. --------------- The line formats are as follows: LINE NUMBERS CONTENTS ------------ -------- 1-7 Array name, array alias, start time, etc. 8 The tape and file numbers of the first master tape to store this file. 11-25 A copy of the APPLE controlling file (c...stn.dat) can be written here if the data has already been processed. 29-92 Up to 64 lines (2 per channel) containing channel information. 93 onwards A listing of the poles and zeros for each different instrument number used in recording the digital data followed by blanks to line 400. The format is the instrument number, number of poles, number of zeros, constant and units on the first line followed by the poles (1 line each) followed by the zeros (1 line each). Normally there should be only 1 or 2 instrument numbers for a file of digital data. 3.1 Line formats in detail All character data are left justified in their fields, all numeric data are right justified. The header initially contains blanks. The value stored in a field if no data are supplied are indicated by "NULL = " e.g NULL = blanks or NULL = -999.0. Some fields are now redundant and have not been described here. ------ LINE 1 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-5 A5 Array ID code Identification code of the array Always present 6-10 A5 Array ID code 2nd identification code of the array Used for the `home' arrays such as EKA, GBA, WRA, YKA, BKN, WOL, FLK, etc Also used to alias IMS codes to ISC codes 11-14 A4 Analogue data Identification code for an analogue array array name NULL = blanks 15-17 'LAT' 18-25 F8.4 Station Units = degrees NULL = -99.0000 latitude 26-29 'LONG' 30-38 F9.4 Station Units = degrees NULL = -999.0000 longitude 39-43 I5 Height Height of station NULL = blanks 44 'M' Units = metres 46-48 A3 Current header This field is always present version Currently = 5.0 50 A1 Start time Due to technical considerations when accurate digitizing analogue data, the start time given is not the actual start time All analogue data is flagged 'N' However, for digital data the start time is the actual start time and flagged 'Y' except in the circumstance of a digital time error when it is flagged as 'N' Always present (Field repeated at LINE 6, Col.1) 51-80 Blank ------ LINE 2 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-8 A8 Event code Agency, event number, or other code 9-10 'Mb' 11-13 F3.1 Magnitude Body wave magnitude NULL = blanks 15-17 'LAT' 18-25 F8.4 Epicentre Units = degrees NULL = -99.0000 latitude 26-29 'LONG' 30-38 F9.4 Epicentre Units = degrees NULL = -999.0000 longitude 39-42 I4 Depth Depth of event NULL = blanks 43-44 'KM' Units = kilometres 45-48 I4 Flinn-Engdahl From 1995 'F-E Code' standard geographic region number 49-80 A32 Flinn-Engdahl Name of the location of the event geographic region name ------ LINE 3 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-11 A11 Event date Date the event in the form dd-mon-yyyy 14-15 'OT' 17-28 A12 Origin time Origin time of event (GMT) in the form hh:mm:ss.tt NULL = blanks 30-31 A2 Code of onset 'AT' = Arrival time as picked by the seismic analyst 'PT' = Picked time as chosen by the data processor 'ET' = Estimated time because either the event not seen or a problem with the time code NULL = blanks 33-44 A12 Start time Start time of event (GMT) in the form hh:mm:ss.tt NULL = blanks 47-54 A8 Phase Phase of event NULL = blanks 55-80 Blank ------ LINE 4 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1 A1 Event type Type of event detected NULL = blank C=Mine explosion E=Chemical explosion I=Collapse explosion M=Meteoric explosion N=Nuclear explosion Q=Earthquake R=Rockburst X=Explosion 2 A1 Effect Event effect NULL = blank C = Casualties D = Damage F = Felt H = Heard T = Tsunami 1-2 A2 Identifier Field can be used for other identifiers NULL = blanks 5-7 'BAZ' 8-14 F7.2 Back bearing Units = degrees NULL = 999.00 Back bearing is defined as the CLOCKWISE angle from the station to the event 17-19 'VEL' 20-25 F6.1 Velocity Units = Km/second NULL = 999.0 28-30 'SLN' 31-36 F6.3 Slowness Units = Second/degree NULL = 99.000 39-43 'DELTA' 44-50 F7.2 Angular Units = degrees NULL = 999.00 distance This is the angle between the event epicentre and the detecting station 51-80 Blank ------ LINE 5 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-20 A20 Start time Start time of the data in the form dd-mmm-yyyy hh:mm:ss NULL = blanks 21-40 A20 End time End time of the data in the form dd-mmm-yyyy hh:mm:ss NULL = blanks 41-48 I8 Total number Number of channels * sample rate (Hz) * of data Number of minutes of data * 60 (in theory) samples Will vary slightly for analogue data Always present 49-50 I2 Number of Number of channels of data data channels Always present 51-63 Digitising Offset time of samples from true digitising Offset rate Usually blank when zero is assumed Units = Seconds 64-80 Comments Usually blank but may contain information taken from a digitised analogue tape ------ LINE 6 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1 A1 Start time Due to technical considerations when accurate digitizing analogue data, the start time given is not the actual start time All analogue data is flagged 'N' However, for digital data the start time is the actual start time and flagged 'Y' except in the circumstance of a digital time error when it is flagged as 'N' Always present (Field repeated from LINE 1, Col.50) 2-9 A8 Raw data type Denotes whether the original recording system was ANALOGUE or DIGITAL Always present 10-29 A20 Original The media the data were ORIGINALLY recorded storage media Possible values are: ANALOGUE TAPE DIGITAL TAPE DIGITAL EXABYTE AUTODRM Always present 30-40 A11 Processing Date the data were edited from raw tape date in the form dd-mon-yyyy Always present 41-80 Blank ------ LINE 7 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-80 A80 Comment Any user comment NULL = blanks For old-style digitised analogue and digital tape this field is a copy of the user label ------ LINE 8 ------ CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-6 I6 Original First tape the data were written tape number 8-10 I3 Original Number of file on this tape file number 11-80 Blank ----------- LINES 11-27 ----------- A copy of the APPLE controlling file used to generate the BKNAS header and data can be inserted here up to 16 lines For a description of this file see either the APPLE subroutine INPUT1 or the read.me file associated with the data ----------- LINES 29-92 ----------- FORMAT OF THE 2 LINES REQUIRED FOR EACH CHANNEL DIGITIZED OR EXTRACTED ---------------------------------------------------------------------- -------------- CHANNEL LINE 1 -------------- CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-5 I5 Channel number Channel number on the raw data tape digitized or extracted Always present 6-11 A6 Pit code ID of the pit associated with this channel NULL = blank 12-14 'LAT' 16-24 F9.5 Pit latitude Units = degrees NULL = -99.00000 25-28 'LONG' 30-39 F10.5 Pit longitude Units = degrees NULL = -999.00000 40 'M' 41-47 F7.1 Pit elevation Units = meters NULL = -999.0 48 'X' 49-56 F8.3 X coord. pit Units = km, measured from the centre of displacement the array NULL = -999.000 57 'Y' 58-65 F8.3 Y coord. pit Units = km, measured from the centre of displacement the array NULL = -999.000 66-70 F5.1 Sample rate Sample rate of the data in samples per second (Hz) Always present 71 A1 Channel sense `+' indicates POSITIVE DIGITS or POSITIVE VOLTAGE = GROUND MOTION UP/NORTH/EAST `-' indicates POSITIVE DIGITS OR POSITIVE VOLTAGE = GROUND MOTION DOWN/SOUTH/WEST Always present 72-80 Blank -------------- CHANNEL LINE 2 -------------- CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-40 A40 Seismometer Type of seismometer in the pit name NULL = blanks 41-44 A4 Seismometer The last letter indicates seismometer output orientation NULL = blanks recorded 50-52 I3 Instrument Instrument number used to record a channel number NULL = INST 999 53-62 A10 Instrument Type of data recorded on the raw data code channel NULL = blanks 63-70 F8.5 Sensitivity Number by which each sampled value is factor multiplied by to obtain the corresponding ground motion in nanometres This is always a positive number and present The sense of the data comes from the channel sense flag in the previous line Units = nm/bit NULL = 1.00000 71-80 Blank ---------------- LINES 93 onwards ---------------- FORMAT OF THE POLES AND ZEROS SECTION ---------------------------------------------------------------------- ---------------------- POLES and ZEROS LINE 1 ---------------------- CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 6-8 I3 Instrument Instrument number used to record a channel number 9-11 I3 Number of poles 12-14 I3 Number of zeros 15-29 E15.4 Poles/zeros NULL = 0.0000E+00 constant 30-61 A32 Units of NULL = blanks constant 62-68 F7.3 Calibration Period in seconds at which sensitivity reference factor (above) is valid NULL = 1.000 70-71 I2 Number of sets If no poles/zeros are inserted this field of poles/zeros is set to zero If there are poles and zeros to insert this field is filled only in the first line of the first pole/zero set 72-80 Blank --------------------------------------------- LINE LISTING A POLE OR ZERO --------------------------------------------- Poles are listed first followed by zeros The poles and zeros are stored as real numbers WITHOUT exponents CHAR FMT FIELD NAME DESCRIPTION ----- ---- --------------- ------------------------------------------ 1-16 E16.* X coordinate X coordinate of a pole or zero 17-32 E16.* Y coordinate Y coordinate of a pole or zero 33-80 Blank ------------------------------ Blank lines follow to line 400 ------------------------------ N.B. Section 4 is not yet available.