IASPEI Seismic Format (ISF)

ISF is the IASPEI approved standard format for the exchange of parametric seismological data (hypocentres, magnitudes, phase arrivals, moment tensors, etc.). It was adopted as standard in August 2001 by IASPEI's Commission on Seismic Observation and Interpretation at the Scientific Assembly in Hanoi, Vietnam. The format is an extenstion of IMS1.0.

Bulletins which use ISF comprise of a series of data blocks. These include a bulletin title block, an event title block, an origin block, a magnitude block, a phase block, etc. An important extension of IMS1.0 is the ability to add comments with keywords refering to specific parametric data. The keywords include PRIME (to designate a prime origin of a hypocentre), CENTROID (to indicate the centroid origin), MOMTENS (moment tensor solution), FAULT_PLANE (fault plane solution), PRINAX (principal axes), PARAM (an origin parameter e.g. hypocentre depth determined by depth phases).

The full documentation is available to download: Source code (in Fortran and C) is provided to read and write ISF data for BULLETIN and ARRIVAL:GROUPED data types:

Example of an ISF Bulletin for a single event (N.B. the data has been modified for illustration purposes) displaying the multiple data blocks available:


IMS1.0/ISF Summary

The following summary provides the formatting required to read or write ISF files for three different data types: Bulletin data; Station data; Arrival data. Please refer to the full documentation for all the available data types and subtypes.

BULLETIN

Bulletins are composed of events, origins and associated arrival information and may include a 'bulletin title', an 'event title', an 'origin block', a 'magnitude sub-block', a 'comment sub-block' and 'phase block'. In addition there are ISF extensions to provide additional data (e.g. moment tensors, fault plane solutions, etc.)

Bulletin title block format

Record Position Format Description
1 1-136 a136 bulletin title

Event title block format

Record Position Format Description
1 1-5 a5 Event
7-14 a8 event identification number
16-80 a65 geographic region

Origin block format

Record Position Format Description
Origin Sub-block
1 4-7 a4 Date
(header) 15-18 a4 Time
27-29 a3 Err
33-35 a3 RMS
37-44 a8 Latitude
46-54 a9 Longitude
57-60 a4 Smaj
63-66 a4 Smin
69-70 a2 Az
72-76 a5 Depth
80-82 a3 Err
84-87 a4 Ndef
89-92 a4 Nst
94-96 a3 Gap
99-103 a5 mdist
106-110 a5 Mdist
112-115 a4 Qual
19-124 a6 Author
131-136 a6 OrigID
Record Position Format Description
1-10 i4,a1,i2,a1,i2 epicenter date (yyyy/mm/dd)
12-22 i2,a1,i2,a1,f5.2 epicenter time (hh:mm:ss.ss)
23 a1 fixed flag (f = fixed origin time solution, blank if not a fixed origin time)
25-29 f5.2 origin time error (seconds; blank if fixed origin time)
31-35 f5.2 root mean square of time residuals (seconds)
37-44 f8.4 latitude (negative for South)
46-54 f9.4 longitude (negative for West)
55 a1 fixed flag (f = fixed epicenter solution, blank if not a fixed epicenter solution)
56-60 f5.1 semi-major axis of 90% ellipse or its estimate (km, blank if fixed epicenter)
62-66 f5.1 semi-minor axis of 90% ellipse or its estimate (km, blank if fixed epicenter)
68-70 i3 strike (0 <= x <= 360) of error ellipse clock-wise from North (degrees)
72-76 f5.1 depth (km)
77 a1 fixed flag (f = fixed depth station, d = depth phases, blank if not a fixed depth)
79-82 f4.1 depth error 90% (km; blank if fixed depth)
84-87 i4 number of defining phases
89-92 i4 number of defining stations
94-96 i3 gap in azimuth coverage (degrees)
98-103 f6.2 distance to closest station (degrees)
105-110 f6.2 distance to furthest station (degrees)
112 a1 analysis type: (a = automatic, m = manual, g = guess)
114 a1 location method: (i = inversion, p = pattern recognition, g = ground truth, o = other)
116-117 a2 event type:
uk = unknown
de = damaging earthquake ( Not standard IMS )
fe = felt earthquake ( Not standard IMS )
ke = known earthquake
se = suspected earthquake
kr = known rockburst
sr = suspected rockburst
ki = known induced event
si = suspected induced event
km = known mine expl.
sm = suspected mine expl.
kh = known chemical expl. ( Not standard IMS )
sh = suspected chemical expl. ( Not standard IMS )
kx = known experimental expl.
sx = suspected experimental expl.
kn = known nuclear expl.
sn = suspected nuclear explosion
ls = landslide
119-127 a9 author of the origin
129-136 a8 origin identification
Record Position Format Description
Magnitude Sub-block
1 1-9 a9 Magnitude
(header) 12-14 a3 Err
16-19 a4 Nsta
21-26 a6 Author
33-38 a6 OrigID
2-n 1-5 a5 magnitude type (mb, Ms, ML, mbmle, msmle)
(data) 6 a1 min max indicator (<, >, or blank)
7-10 f4.1 magnitude value
12-14 f3.1 standard magnitude error
16-19 i4 number of stations used to calculate magni-tude
21-29 a9 author of the origin
31-38 a8 origin identification
Record Position Format Description
Comment Sub-block
1 2 a1 (
3-M a(M-2) comment
M+1 a1 )

Phase block format

Record Position Format Description
1 1-3 a3 Sta
(header) 9-12 a4 Dist
15-18 a4 EvAz
20-24 a5 Phase
33-36 a4 Time
43-46 a4 TRes
49-52 a4 Azim
54-58 a5 AzRes
62-65 a4 Slow
69-72 a4 SRes
74-76 a3 Def
80-82 a3 SNR
90-92 a3 Amp
96-98 a3 Per
100-103 a4 Qual
105-113 a9 Magnitude
118-122 a5 ArrID
Record Position Format Description
2-n 1-5 a5 station code
(data) 7-12 f6.2 station-to-event distance (degrees)
14-18 f5.1 event-to-station azimuth (degrees)
20-27 a8 phase code
29-40 i2,a1,i2,a1,f6.3 arrival time (hh:mm:ss.sss)
42-46 f5.1 time residual (seconds)
48-52 f5.1 observed azimuth (degrees)
54-58 f5.1 azimuth residual (degrees)
60-65 f5.1 observed slowness (seconds/degree)
67-72 f5.1 slowness residual (seconds/degree)
74 a1 time defining flag (T or _)
75 a1 azimuth defining flag (A or _)
76 a1 slowness defining flag (S or _)
78-82 f5.1 signal-to-noise ratio
84-92 f9.1 amplitude (nanometers)
94-98 f5.2 period (seconds)
100 a1 type of pick (a = automatic, m = manual)
101 a1 direction of short period motion (c = compression, d = dilatation, _= null)
102 a1 onset quality (i = impulsive, e = emergent, q = questionable, _ = null)
104-108 a5 magnitude type (mb, Ms, ML, mbmle, msmle)
109 a1 min max indicator (<, >, or blank)
110-113 f4.1 magnitude value
115-122 a8 arrival identification
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Moment Tensor Origin Comments

Each moment tensor report is comprised of two header lines and a variable number of pairs of data lines. All of the moment tensors in one report are for the same origin, which precedes the report. Several items are omitted: "Centroid, since it is presumed to precede in an origin line. "The best fitting double-couple, since it could follow as a FAULT_PLANE comment. "Principal axes, since they could follow as a PRINAX comment. "MW, since it could be included in the magnitude sub-block associated with the event. Several redundant items are included: "All three diagonal elements of the moment tensor are included since non-isotropic moment tensors may be reported occasionally "Scalar moment, fraction CLVD and their uncertainties are included since these may be the most frequently used moment tensor parameters.

Table: Formatted Moment Tensor Comment

Record Position Format Description
1 3-10 a8 #MOMTENS
Header 12-13 a2 sc
18-19 M0
21-25 fCLVD
30-32 MRR
37-39 MTT
44-46 MPP
51-53 MRT
58-60 MTP
65-67 MPR
69-72 NST1
74-77 NST2
79-84 Author
Record Position Format Description
2 3 a1 #
(header) 17-19 a3 eM0
21-25 a5 eCLVD
30-32 a3 eRR
37-39 a3 eTT
44-46 a3 ePP
51-53 a3 eRT
58-60 a3 eTP
65-67 a3 ePR
69-72 a4 NCO1
74-77 a4 NCO2
79-86 a8 Duration
Record Position Format Description
3 3 a1 #
(data) 12-13 i2 scale factor (log10 of number by which moment tensor components and their uncertainties must be multiplied to obtain Newton-meters)
15-19 f5.3 scalar seismic moment
21-25 f5.3 fraction of moment released as a compensated linear vector dipole
27-32 f6.3 radial-radial element of moment tensor
34-39 f6.3 theta-theta element of moment tensor
41-46 f6.3 phi-phi element of moment tensor
48-53 f6.3 radial-theta element of moment tensor
55-60 f6.3 theta-phi element of moment tensor
62-67 f6.3 phi-radial element of moment tensor
69-72 i4 number of stations used, type 1 (Body wave for HRVD)
74-77 i4 number of stations used, type 2 (Mantle or Surface wave for HRVD)
79-87 a9 agency that computed the moment tensor
Record Position Format Description
4 3 a1 #
(data) 15-19 f5.3 uncertainty of scalar seismic moment
21-25 f5.3 uncertainty of fCLVD
27-32 f6.3 uncertainty of radial-radial element
34-39 f6.3 uncertainty of theta-theta element
41-46 f6.3 uncertainty of phi-phi element
48-53 f6.3 uncertainty of radial-theta element
55-60 f6.3 uncertainty of theta-phi element
62-67 f6.3 uncertainty of phi-radial element
69-72 i4 number of components used, type 1
74-77 i4 number of components used, type 2
79-86 f8.2 presumed or computed source duration (seconds)
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Fault Plane Solution Origin Comments

Either one plane or two may be given.

Table: Fault Plane Solution Origin Comment

Record Position Format Description
1 3-14 a12 #FAULT_PLANE
(header) 16-18 a3 Typ
20-25 a6 Strike
29-31 a3 Dip
36-39 a4 Rake
42-44 a2 NP
46-47 a2 NS
49-53 a5 Plane
55-60 a6 Author
Record Position Format Description
2 3 a1 # first plane, + second plane
(data) 16-18 a3 Fault plane solution computed from:
FM = first motions
BDC = best double couple
20-25 f6.3 Strike of either nodal plane (degrees, 0 to 360)
27-31 f5.3 Dip of the same nodal plane (degrees, 0 to 90)
33-39 f7.3 Rake of slip vector in the described plane (degrees, -180 to +180; required if only one plane is given)
41-43 i3 number of P polarities (not required for type BDC)
45-47 i3 number of S polarisations (not required for type BDC)
49-53 a5 Plane identification: AUXIL = this is the auxiliary plane = neither plane is preferred at the fault
FAULT = this is the preferred fault plane
AUXIL = this is the auxiliary plane
55-62 a8 agency that computed the fault plane solution (neither required nor paresd for second plane)
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Principal Axes Origin Comments

Principal axes can be computed from either a moment tensor or a fault plane solution. A bulletin may include the principal axes alone, or as well as the moment tensor or fault plane solution from which they were computed. Principal values are optional since they may not be available if the principal axes are computed from a fault plane solution based on first motions. The error header and error lines are each optional. ISPF writers should write the error header if the error data line is written. ISPF parsers should be able to parse the error line regardless of whether or not the error header line is present.

Table: Formatted Principal Axes Origin Comment

Record Position Format Description
1 3-9 a7 #PRINAX
(header) 11-12 a2 sc
15-19 a5 T_val
21-26 a6 T_azim
29-32 a4 T_pl
35-39 a5 B_val
41-46 a6 B_azim
49-52 a4 B_pl
55-59 a5 P_val
61-66 a6 P_azim
69-72 a4 P_pl
74-79 a6 Author
Record Position Format Description
2 2 a1 +
(header) 17-19 a3 eTv
24-26 a3 eTa
30-32 a3 eTp
37-39 a3 eBv
44-46 a3 eBa
49-52 a3 eBp
57-59 a3 ePv
64-66 a3 ePa
70-72 a3 ePp
74-78 a5 fCLVD
Record Position Format Description
3 3 a1 #
(data) 11-12 i2 scale factor (log10 of number by which moment tensor components and their uncertainties must be multiplied to obtain Newton-meters; optional)
14-19 f6.3 largest principal value (optional)
21-26 f6.2 largest principal value axis azimuth
28-32 f5.2 largest principal value axis plunge
34-39 f6.3 middle principal value (optional)
41-46 f6.2 middle principal value axis azimuth
48-52 f5.2 middle principal value axis plunge
54-59 f6.3 smallest principal value (optional)
61-66 f6.2 smallest principal value axis azimuth
68-72 f5.2 smallest principal value axis plunge
74-81 a8 agency that computed the principal axes
Record Position Format Description
4 3 a1 #
(data) 15-19 f5.3 uncertainty of T principal value (optional)
22-26 f5.2 uncertainty of T axis azimuth
28-32 f5.2 uncertainty of T axis plunge
35-39 f5.3 uncertainty of B principal value (optional)
42-46 f5.2 uncertainty of B axis azimuth
48-52 f5.2 uncertainty of B axis plunge
55-59 f5.3 uncertainty of P principal value (optional)
62-66 f5.2 uncertainty of P axis azimuth
68-72 f5.2 uncertainty of P axis plunge
74-78 f5.3 fraction of the moment release as compensated linear vector dipole (optional)
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Additional Parameter Origin Comments

After the keyword PARAM, each origin parameter comment consists of a set of names from the MSOP list of earthquake parameters followed by an equal sign and a value. Spaces are not allowed before or after the equal sign, but are instead reserved as a separator between measurements. Units are not given for the measurements, but specified for each standard measurement name (e.g., STRESS_DROP must be given in Pascals). Values must be stated as real numbers including a decimal point and may include an exponent, indicated by an upper-case E , e.g., 1.0E27.

Table: Formatted Additional Parameter Origin Comment

Record Position Format Description
1 3-8 a6 #PARAM
(data) 10-89 a80 NAME=VALUE NAME=VALUE ....

Table: Preliminary List of Additional Origin Parameters

Name Units Description
STRESS_DROP Pascals
SCALAR_MOMENT Newton-meters
SEISMIC_ENERGY Joules
pP_DEPTH Kilometers
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Bibliographic Citations

Prior to 1996 the ISC bibliography provided a link between events and research papers associated with them. This data block reproduces the ISC bibliography.

Table: Bibliographic Citations

Record Position Format Description
1 1-4 a12 Year
(header) 6-11 a3 Volume
13-17 a6 Page1
19-23 a3 Page2
25- a4 Journal
Record Position Format Description
2 1-4 i4 Year of publication
(data) 6-11 a6 Volume
13-17 i5 Start page
19-23 i5 End page
25-104 a80 Journal title
Record Position Format Description
Comment Sub-block
1 2-10 a9 (#AUTHORS
(data) 11-90 a80 Author , author ... author.
92 a1 )
2-n 2-3 a2 (+
(continuation) 11-90 a80 Author , author ... author.
92 a1 )
Record Position Format Description
Comment Sub-block
1 2-8 a7 (#TITLE
(data) 11-90 a80 Title.
92 a1 )
2-n 2-3 a2 (+
(continuation) 11-90 a80 Title
92 a1 )

STATION

The STATION data type is used to describe the site, location, and dates of operation for stations.

Station block format

Record Position Format Description
1 1-3 a3 Net
(header) 15-18 a3 Sta
27-29 a4 Type
33-35 a8 Latitude
37-44 a9 Longitude
46-54 a9 Coord Sys
57-60 a4 Elev
63-66 a7 On Date
63-66 a8 Off Date
2-n 1-9 a9 network code
(data) 11-15 a5 station code
17-20 a4 1c = single component
3c = three component
hfa = high-frequency array
lpa = long-period array
22-30 f9.5 latitude (negative for South)
32-41 f10.5 longitude (negative for West)
43-54 a12 coordinate system (for example, WGS-84)
56-60 f5.3 elevation (km)
62-71 i4,a1,i2,a1,i2 start date of station operation (yyyy/mm/dd)
73-82 i4,a1,i2,a1,i2 end of station operation (yyyy/mm/dd)

ARRIVAL

The ARRIVAL data type is divided into five subtypes (automatic, reviewed, grouped, associated, and unassociated). The grouped arrival format is shown below. Please refer to the documentation for details on the other subtypes.

Grouped arrival format

The grouped subtype is used for arrivals that have phase names and have been grouped together, with the implication that they were generated by the same seismic event.

Record Position Format Description
1 1-3 a3 Net
(header) 11-13 a3 Sta
16-19 a4 Chan
21-23 a3 Aux
29-32 a4 Date
39-42 a4 Time
50-54 a5 Phase
60-63 a4 Azim
66-69 a4 Slow
73-75 a3 SNR
83-85 a3 Amp
89-91 a3 Per
93-96 a4 Qual
100-104 a5 Group
106 a1 C
108-113 a6 Author
121-125 a5 ArrID
Record Position Format Description
2-n 1-9 a9 network code
(data) 11-15 a5 station code
17-19 a3 FDSN channel code
21-24 a4 auxiliary identification code
26-35 i4,a1,i2,a1,i2 arrival date (yyyy/mm/dd)
37-48 i2,a1,i2,a1,f6.3 arrival time (hh:mm:ss.sss)
50-57 a8 phase code
59-63 f5.1 observed azimuth (degrees)
65-69 f5.1 observed slowness (seconds/degree)
71-75 f5.1 signal-to-noise ratio
77-85 f9.1 amplitude (nanometers)
87-91 f5.2 period (seconds)
93 a1 type of pick (a = automatic, m = manual)
94 a1 direction of short period motion (c = compression, d = dilatation, _= null)
95 a1 detection quality (i = impulsive, e = emergent, q = questionable, _ = null)
97-104 a8 group identification
106 i1 conflict flag (number of times an arrival belongs to more than one group; leave blank if arrival only belongs to one group)
108-116 a9 author of the arrival
118-125 a8 arrival identification