Quake

The Quake submodule was introduced in SeisIO v0.3.0 to isolate handling of discrete earthquake events from handling of continuous geophysical data. While the channel data are similar, fully describing an earthquake event requires many additional Types (objects) and more information (fields) in channel descriptors.

Types

See Type help text for field descriptions and SeisIO behavior.

EQMag()

Earthquake magnitude object.

EQLoc()

Structure to hold computed earthquake location data.

EventChannel()

A single channel of trace data (digital seismograms) associated with a discrete event (earthquake).

EventTraceData()

A custom structure designed to describe trace data (digital seismograms) associated with a discrete event (earthquake).

PhaseCat()

A seismic phase catalog is a dictionary with phase names for keys (e.g. “pP”, “PKP”) and SeisPha objects for values.

SeisEvent()

A compound Type comprising a SeisHdr (event header), SeisSrc (source process), and EventTraceData (digital seismograms.)

SeisHdr()

Earthquake event header object.

SeisPha()

A description of a seismic phase measured on a data channel.

SeisSrc()

Seismic source process description.

SourceTime()

QuakeML-compliant seismic source-time parameterization.

Web Queries

Keyword descriptions for web queries appear at the end of this section.

FDSNevq(ot)

Event header query. Multi-server query for the event(s) with origin time(s) closest to ot. Returns a tuple consisting of an Array{SeisHdr,1} and an Array{SeisSrc,1}, so that the i`th entry of each array describes the header and source process of event `i.

Keywords: evw, mag, nev, rad, reg, src, to, v

Notes

  • Specify ot as a string formatted YYYY-MM-DDThh:mm:ss in UTC (e.g. “2001-02-08T18:54:32”).
  • Incomplete string queries are read to the nearest fully-specified time constraint; thus, FDSNevq(“2001-02-08”) returns the nearest event to 2001-02-08T00:00:00.
  • If no event is found in the specified search window, FDSNevq exits with an error.
  • For FDSNevq, keyword src can be a comma-delineated list of sources, provided each has a value in ?seis_www; for example, src="IRIS, INGV, NCEDC" is valid.
FDSNevt(ot::String, chans::String)

Get header and trace data for the event closest to origin time ot on channels chans. Returns a SeisEvent structure.

Keywords: evw, fmt, len, mag, model, nd, opts, pha, rad, reg, src, to, v, w

Notes

  • Specify ot as a string formatted YYYY-MM-DDThh:mm:ss in UTC (e.g. “2001-02-08T18:54:32”).
  • Incomplete string queries are read to the nearest fully-specified time constraint; thus, FDSNevq(“2001-02-08”) returns the nearest event to 2001-02-08T00:00:00.
  • If no event is found in the specified search window, FDSNevt exits with an error.
  • Unlike FDSNevq, number of events cannot be specified and src must be a single source String in ?seis_www.


get_pha!(S::Data[, keywords])

Command-line interface to IRIS online travel time calculator, which calls TauP. Returns a matrix of strings.

Keywords: pha, model, to, v

References

  1. TauP manual: http://www.seis.sc.edu/downloads/TauP/taup.pdf
  2. Crotwell, H. P., Owens, T. J., & Ritsema, J. (1999). The TauP Toolkit: Flexible seismic travel-time and ray-path utilities, SRL 70(2), 154-160.

Web Query Keywords

KW Default T [1] Meaning
evw [600.0, 600.0] A{F,1} search window in seconds [2]
fmt “miniseed” S request data format
len 120.0 I desired trace length [s]
mag [6.0, 9.9] A{F,1} magnitude range for queries
model “iasp91” S Earth velocity model for phase times
nd 1 I number of days per subrequest
nev 0 I number of events returned per query [3]
opts “” S user-specified options [4]
pha “P” S phases to get [5]
rad [] A{F,1} radial search region [6]
reg [] A{F,1} rectangular search region [7]
src “IRIS” S data source; type ?seis_www for list
to 30 I read timeout for web requests [s]
v 0 I verbosity
w false B write requests to disk? [8]

Table Footnotes

[1]Types: A = Array, B = Boolean, C = Char, DT = DateTime, F = Float, I = Integer, S = String, U8 = Unsigned 8-bit integer (UInt8)
[2]search range is always ot-|evw[1]| ≤ t ≤ ot+|evw[2]|
[3]nev=0 returns all events in the query
[4]String is passed as-is, e.g. “szsrecs=true&repo=realtime” for FDSN. String should not begin with an ampersand.
[5]Comma-separated String, like “P, pP”; use “ttall” for all phases
[6]Specify region [center_lat, center_lon, min_radius, max_radius, dep_min, dep_max], with lat, lon, and radius in decimal degrees (°) and depth in km with + = down. Depths are only used for earthquake searches.
[7]Specify region [lat_min, lat_max, lon_min, lon_max, dep_min, dep_max], with lat, lon in decimal degrees (°) and depth in km with + = down. Depths are only used for earthquake searches.
[8]If w=true, a file name is automatically generated from the request parameters, in addition to parsing data to a SeisData structure. Files are created from the raw download even if data processing fails, in contrast to get_data(… wsac=true).

Example

Get seismic and strainmeter records for the P-wave of the Tohoku-Oki great earthquake on two borehole stations and write to native SeisData format:

S = FDSNevt("201103110547", "PB.B004..EH?,PB.B004..BS?,PB.B001..BS?,PB.B001..EH?")
wseis("201103110547_evt.seis", S)

Utility Functions

distaz!(Ev::SeisEvent)

Compute distance, azimuth, and backazimuth by the Haversine formula. Overwrites Ev.data.dist, Ev.data.az, and Ev.data.baz.

gcdist([lat_src, lon_src, ]rec)

Compute great circle distance, azimuth, and backazimuth from a single source with coordinates [s_lat, s_lon] to receivers rec with coordinates [r_lat r_lon] in each row.

show_phases(P::PhaseCat)

Formatted display of seismic phases in dictionary P.

fill_sac_evh!(Ev::SeisEvent, fname[; k=N])

Fill (overwrite) values in Ev.hdr with data from SAC file fname. Keyword k=i specifies the reference channel i from which the absolute origin time Ev.hdr.ot is set. Potentially affects header fields :id, :loc (subfields .lat, .lon, .dep only), and :ot.

Reading Earthquake Data Files

S = read_quake(fmt::String, filename [, KWs])
Read data in file fmt from file filename into memory.

fmt
Case-sensitive string describing the file format. See below.

KWs
Keyword arguments; see also SeisIO standard KWs or type ?SeisIO.KW.
Standard keywords: full, nx_add, nx_new, v
Other keywords: See below.

Supported File Formats

File Format String Notes
PC-SUDS suds  
QuakeML qml, quakeml only reads first event from file
UW uw  

Supported Keywords

KW Used By Type Default Meaning
full suds, uw Bool false read full header into :misc?
v all Integer 0 verbosity

QuakeML

read_qml(fpat::String)

Read QuakeML files matching string pattern fpat. Returns a tuple containing an array of SeisHdr objects H and an array of SeisSrc objects R. Each pair (H[i], R[i]) describes the preferred location (origin, SeisHdr) and event source (focal mechanism or moment tensor, SeisSrc) of event i.

If multiple focal mechanisms, locations, or magnitudes are present in a single Event element of the XML file(s), the following rules are used to select one of each per event:

FocalMechanism
1. preferredFocalMechanismID if present
2. Solution with best-fitting moment tensor
3. First FocalMechanism element

Magnitude
1. preferredMagnitudeID if present
2. Magnitude whose ID matches MomentTensor/derivedOriginID
3. Last moment magnitude (lowercase scale name begins with “mw”)
4. First Magnitude element

Origin
1. preferredOriginID if present
2. derivedOriginID from the chosen MomentTensor element
3. First Origin element

Non-essential QuakeML data are saved to misc in each SeisHdr or SeisSrc object as appropriate.

write_qml(fname, Ev::SeisEvent; v::Integer=0)

See writing.