Frequently Asked Questions
Answers are sorted into the following categories:
- Data
01 What type of data
is handled by IRIS?
02 From what sources does the DMC get its
data?
03 In what format is data at the DMC stored?
04 Why is there restricted access to some
of the data at the DMC?
05 How do I request restricted data?
06 How do I tell what data is available
from the DMC?
07 I made a request for data shortly after
an event and I got the "no data" message. How do I get data
within hours of an event?
08 How do I get station response information?
09 What is the difference between assembled
and customized data?
10 I need to know what stations were recording
data during a specific event. How do I do that?
11 I only want data from stations that
are a certain distance from an event. How do I do that?
12 I received a "no data" message
when requesting data from the DMC but I checked the database and I know
that the station was running at the time for which I requested data. What
went wrong?
13 I see that the instrument response
in RESP and SAC file formats is slightly different in the Poles and Zeroes
section. In the SAC file, there is an additional "one zero".
Is the SAC response file automatically converted by rdseed to displacement?
Most instrument responses are reported in velocity, do all SAC responses
have one additional zero?
14 How do I get data out of a miniSEED
volume?
15 I downloaded data in SAC fromat. Is
the unit of dependent variable in the data mm/sec or nm/sec or mm/sec/sec,
etc?
16 I downloaded some PASSCAL SEG-Y data.
What do I do with it?
17 What does the D, R, or Q character
mean in my data file name?
- Request Methods
01 How do
I know which request tool to use?
02 When making a BREQ_FAST
request, do I have to include a network code?
03 What is a location
identifier (or location code)?
04 Why do some of my
data files include some extra characters or double periods between the network
code and channel code in the file name?
05 I received a "no data" message
when requesting data from the DMC but I checked the database
and I know that the station was running at the time for which
I requested data. What went wrong?
- IRIS supported software
01 When
I try to run rdseed, I get an error message. What do I do?
02 How do I know if
I'm running the latest version of software?
03 When running
WEED, I get the following error message: "Error -Unable to start rdseed_weed.
Check path."
05 Does IRIS have software tutorials?
04 I am downloading
a file through ftp that has '.tar' in the filename. What does this mean
and what do I do with it?
- General IRIS questions
01 Who is
allowed to join IRIS?
02 How does my institution become a member of IRIS?
03 What does IRIS stand for?
- Data Management System
01 Who runs the DMS?
- Education & Outreach
01 I am curious about the Richter scale.
Some books tell me that each successive number increases the
power of an earthquake by a factor of 32, others say it is
10. Which is it?
02 When I look at a list of earthquakes,
I see that there are different letters after the magnitude.
What are they for?
03 Is the occurence of earthquakes effected
by the eruption of volcanoes?
04 How do I look for a job in Seismology?
- GSN
01 What stations
are part of the GSN?
- PASSCAL and
Instrumentation
Data Questions
- Q01. What type of data is handled
by IRIS?
- The Data
Management System of IRIS is tasked with archiving seismic
data from many sources. Most of the data stored at the Data
Management Center in Seattle can be categorized as passive source
seismic data collected by broad-band instruments. However, the
DMC also stores some active source data and data from non-seismic
instruments.
-
- Q02. From what sources does the DMC
get its data?
- The DMC is responsible for data from a number
of international and regional networks, both temporary and permanent.
To see a list of networks that contribute (or intend to contribute)
data to the DMC, look here:
-
- Q03. In what format is data at the
DMC stored?
- All data stored in the DMC's RDBMS (Relational
Database Management System) arrives to the DMC in SEEDv2.4 format.
Much of the PASSCAL data is also in SEED format but some are
in other formats such as SEG-Y, SAC or AH. To see which format
has been used for a temporary deployment (PASSCAL or other),
view the assembled
data sets and/or the temporary
network listings.
-
- Q04. Why is there restricted access
to some of the data at the DMC?
- Data from PASSCAL
(and some other temporary deployments) are subject to a two
year moratorium, allowing the PI's who proposed the scientific
study the opportunity to report and publish results. To do this
we have enabled exclusive access to designated endusers, where
the experiment PI's have the option of releasing the data to
registered users to whom they have given permission (or to everyone)
whenever they choose but they have at least 2 full years
from the end date of the experiment before they are
required to release the data to the general user population.
-
- Q05. How do I request restricted data?
- You must contact one of the experiment's Principle
Investigators (PIs) and get a password. You can find the names
of participating PIs by viewing the meta data for experiments
using SeismiQuery (assembled
or temporary networks
query). Once you have the password, you must register
as a restricted user. Use any of the standard requests
tools provided by the DMC to make your data request. The
data is encrypted using the UNIX utility 'crypt', with the same
password given to the PI.
-
- Q06. How do I tell what data is available
from the DMC?
- The best way to check on data availability is to use our on-line
database access tool SeismiQuery.
SeismiQuery offers several different query tools to assist the
user in acquiring information about data availability as well
as meta data about stations, channels and event catalogs.
-
- Q07. I made a request for data shortly
after an event and I got the "no data" message. How
do I get data within hours of an event?
- SPYDER® is our near-real-time data retrieval system. SPYDER®
data is not QCed but is available almost immediately after an
event. To browse and request SPYDER® data, use WILBER
II — our Web-based request tool.
-
- Q08. How do I get station response
information?
- Station response information is part of the SEED
data format. You can extract responses from a SEED volume using
rdseed OR you
can view response information directly from the database using
SeismiQuery.
For users familiar with the BREQ_FAST
request format, a BREQ_FAST request can be sent to DATALESS@iris.edu
to request a dataless SEED file containing meta data for the
requested station/channel/time spans.
For BUD
users, the BUD Query Interface now offers the option of requesting
a dataless SEED file after data selection has been done that
is specific for the data selected. A dataless SEED file for
all channels in BUD is available via ftp. View more documentation
on this on the BUD start page.
-
- Q09. What is the difference between
assembled and customized data?
- Some data comes to the DMC in a format other than SEED,
such as SEG-Y or SAC. These data are considered "assembled"
because they are unique to a project or experiment and are not
archived on the mass storage system like SEED data is archived.
Users request this data via e-mail to assembled_request@iris.edu
and may request all or part of the data set. One could also
consider FARM data (in SEED format) as assembled because all
data within a given FARM volume are related to a specific event
and the data can be downloaded via ftp without having the user
make a formal (or customized) request. A "customized"
request is a request made for data that comes out of the general
SEED archive (mass storage) and is customized to meet, as closely
as possible, the user's specified parameters.
-
- Q10. I need to know what stations
were recording data during a specific event. How do I do that?
- Use the by
timeseries tool in SeismiQuery.
You need only set a time period and wildcard the network (using
the % sign as the wildcard character) and the rest of the parameters
will be "wildcarded" for you. As a result, you can
view a graph or table of all stations/channels for which data
was archived during the specified time period. (It uses the
GOAT
tool to display information.) If you just want to see timeseries
information for a specific station or network, use the by
station or by
network tool, respectively. The result from either
of those two queries is a yearly calendar with days of availability
highlighted and linked to a more complete timeseries table.
-
- Q11. I only want data from stations
that are a certain distance from an event. How do I do that?
- Use WEED. WEED
is an x-windows request tool that allows you to set very specific
parameters for requesting event-related data. By using the "Extraction
Parameters" window within WEED, you can set up a station
"window" so only those stations that fall within the
distance set are included in your request.
-
- Q12. I received a "no data"
message when requesting data from the DMC but I checked the
database and I know that the station was running at the time
for which I requested data. What went wrong?
- First of all, checking the database is the right thing to
do. However, if you only checked for station up-time you may
have gotten a false impression about data availability. The
information you can get by using the channels or stations
queries (within SeismiQuery)
is meta data only and does not necessarily reflect what data
has actually been archived at the DMC. A better way to check
on data availability is to use the by
timeseries, by
station, or by
network query within SeismiQuery. The views that are
created when using the 'by timeseries, by station, or by network'
tabs are looking into the waveform timeseries tables, indicating
to a user exactly what data is available, and eliminates the
confusion about when a station was running but returning no
data.
-
- Q13. I see that the instrument response
in RESP and SAC file formats is slightly different in the Poles
and Zeroes section. In the SAC file, there is an additional
"one zero". Is the SAC response file automatically
converted by rdseed to displacement? Most instrument responses
are reported in velocity, do all SAC responses have one additional
zero?
- SAC by
default assumes that ground motion is in terms of displacement.
Most of the IRIS era data responses are given in velocity units,
so yes rdseed
adjusts the poles and zero file output for SAC so that the units
are displacement. It also makes the required 2xpi adjustments
when poles/zeroes are given in hertz rather than radians/s.
-
- Q14. How do I get data out of a miniSEED
volume?
- MiniSEED volumes (station/channel waveform data only) need
a dataless SEED volume (meta data only) in order for a user
to extract data. (Think of the dataless volume as the head and
the miniSEED as the body.) The application rdseed is used to
make this suture. Here is an extract from the rdseed
manual about how to put these two files together in order
to get at the data:
|
The user can specify that station configuration and responses
be taken from another SEED volume. This will allow for
two possible scenarios to be accomplished. First, if station
information is found to be in error, the user can use
the headers from another SEED volume that is known to
be correct. Second, if the SEED volume is a "data-only"
volume (miniSEED), the user can use a "data-less"
SEED volume and the "data-only" SEED volume
to extract the desired waveforms. So you say, "how
do I do this?". The environment variable ALT_RESPONSE_FILE
should be defined with its value being the path name of
the SEED volume from which responses should be taken. |
-
- Q15. I downloaded data in SAC fromat.
Is the unit of dependent variable in the data mm/sec or nm/sec
or mm/sec/sec, etc?
- The units of displacement vary, depending upon the instrument
response values and sensor type. These units are listed in the
SEED volumes that you receive from us, and are available from
the output of the program 'rdseed' using the -R option. This
option writes files that we call instrument response files,
and look like RESP.PS.BAG..BHE, for example. If you look at
this file, you will see listed something like this:
# =======================================
# + +--------------------------------------------+ +
# + | Response (Poles & Zeros), BAG ch BHE | +
# + +--------------------------------------------+ +
#
B053F03 Transfer function type: A [Laplace Transform (Rad/sec)]
B053F04 Stage sequence number: 1
B053F05 Response in units lookup: M/S - Velocity in Meters Per Second
B053F06 Response out units lookup: V - Volts
B053F07 A0 normalization factor: 3948.58
B053F08 Normalization frequency: 0.02
B053F09 Number of zeroes: 2
B053F14 Number of poles: 4
where you will see that for this channel, it's stated as velocity,
in meters/second. Others may be acceleration or displacement.
-
- Q16. I downloaded some PASSCAL SEG-Y
data. What do I do with it?
- For an overview of what programs we have that work with SEG-Y
(& other formats):
http://www.passcal.nmt.edu/software/segy.html
For a definition of SEG-Y format (PASSCAL & standard):
http://www.passcal.nmt.edu/software/segy.html
-
- Q17. What does the D, R, or Q character
mean in my data file name?
- This is a quality control marker.
Q = Data tagged as QC'd
D = Data of indeterminate quality
R = Raw Data at the DMC
For more details about the markers and how you can costumize
your data requests, please view this DMC newsletter article:
http://www.iris.edu/news/newsletter/vol4no2/page1.htm
Request Method Questions
- Q01. How do I know which request
tool to use?
- The DMC offers many different tools for making requests because
our user community is so diverse. There is a Data
Access Tutorial that covers all tools and the reasons for
using them. If you still have questions after reviewing the
tutorial, feel free to send those questions to comments@iris.edu.
-
- Q02. When making a BREQ_FAST request,
do I have to include a network code?
- No, but if you use a wildcard for network code if you do not
specify the network code, you will get data returned from all
of our holdings that match the other delimiters on the request
line. Please check the BREQ_FAST
manual for details.
-
- Q03. What is a location identifier
(or location code)?
- The use of location codes enables the distinction between
multiple same-name channels from different, co-located sensors
at one site.There is an article
in one of the DMC Electronic Newsletters that explains the use
of location identifiers.
-
- Q04. Why do some of my data files
include some extra characters or double periods between the
network code and channel code in the file name?
- In 1998, the DMC began using location
identifiers to uniquely identify a data stream among many
data streams for the same channel id and station id.
EXAMPLES: ANMO.IU.00.BHZ.xxxx and ANMO.IU.10.BHZ.xxxx
means there are two different instruments at the ANMO sight
that use the BHZ channel designation. (For more information
about how location identifiers are applied, please read this
DMC
Electronic Newsletter article.)
If a station does not use location identifiers, the file name
will look something like this: ANMO.IU..LHN.xxxx. To see if
there are location identifiers used for a particular installation,
use SeismiQuery
(channels query) and be sure to check "location" to
include this field in your query.
-
- Q05. I received a "no data"
message when requesting data from the DMC but I checked the
database and I know that the station was running at the time
for which I requested data. What went wrong?
- First of all, checking the database is the right thing to
do. However, if you only checked for station up-time you may
have gotten a false impression about data availability. The
information you can get by using the channels or stations
queries (within SeismiQuery)
is meta data only and does not necessarily reflect what data
has actually been archived at the DMC. A better way to check
on data availability is to use the by
timeseries, by
station, or by
network query within SeismiQuery. These queries return
start and end time values so you know exactly what timeseries
data is available.
-
IRIS supported software questions
- Q01. When I try to run rdseed, I
get an error message. What do I do?
- First, check to make sure that you are running the most recent version
of rdseed. If
not, download
the newer version. If you have the newest version and you still
get an error message, you may have a bad SEED volume. All SEED
volumes are checked before they are sent out or put into the
ftp directory but SEED volumes can "go bad" if the
data transfer is stopped prematurely. Check the SEED volume
size. If you still get an error message, send an e-mail to comments@iris.edu.
-
- Q02. How do I know if I'm running the latest
version of software?
- At this time, IRIS does not have a way of performing auto-updates of its
supported software packages. The best way to check on the latest version
numbers is to look in our ftp directory:
ftp://ftp.iris.washington.edu/pub/programs
-
- Q03. When running WEED, I get the following
error message: "Error -Unable to start rdseed_weed. Check
path".
- Make sure your PATH environment variable is set to this directory; the
directory you copied rdseed into.
EXAMPLE:setenv PATH $PATH:/the_dir_where_rdseed_lies
The WEED_HOME environment variable is optional. If you set it,
WEED will look
there for its system files, IASPEI tables, event, station, phase
files, etc.
-
- Q04: I am downloading a file through ftp that
has '.tar' in the filename. What does this mean and what do
I do with it?
- This is the Tape ARchive file format that is commonly used to bundle multiple
files and directories into a single downloadable file. When downloading
a tar file, be sure to set your ftp client to download binary
data. This can be performed by typing BIN
as a command if you are using a text-based FTP client. Then download the
file a directory where you want to extract the data.
To open the tar file, use the Unix tar command. First, you might
want to look at the contents of the tar file. This example shows how to
look at the contents of 'myfile.tar':
tar tvf myfile.tar
You will see a listing of files and possibly directory names, and it will
indicate where the files in the tar file will be extracted. Note that this
does not yet write any files to your disk, so it is safe and good practice
to use.
You will want to verify that the files will extract to the place you want
them. If the directory names in the tar file begin with a slash '/' instead
of a dot '.' or directory name, it is advised that you think twice about
extracting the files, especially if you are running as a privileged user.
The reason for this is that the leading slash means the files will be extracted
off of your system's root directory and could delete or replace vital system
files. It is considered bad practice to have directory names with leading
slashes in a tar file.
When you feel confident about where the files will be extracted, use the
command:
tar xvf myfile.tar
to extract the files. If you have any questions, send e-mail to comments@iris.edu.
- Q05. Does IRIS have software tutorials?
- Yes, IRIS is developing software tutorials for JWEED, VASE and other
applications. Online software tutorials are available at:
http://www.iris.edu/tutorials/
General IRIS questions
- Q01. Who is allowed to join IRIS?
- Educational and not-for-profit institutions chartered in the US, with
a major commitment to research in seismology and related fields, may become
members. Research institutions and other not-for-profit organizations both
inside and outside the US engaged in seismological research and development,
which do not otherwise qualify for IRIS membership, may be elected affiliates
or foreign affiliates.
-
- Q02. How does my institution become a member
of IRIS?
- Fill out this simple form
and information will be sent to you.
-
- Q03. What does IRIS stand for?
- IRIS is an acronym for Incorporated Research Institutions for Seismology.
Data Management System questions
- Q01. Who runs the DMS?
- The IRIS DMS is given oversight by a standing
committee representing the seismological community. The
DMS is managed by Dr. Tim Ahern at the Data
Management Center in Seattle, WA.
-
Education & Outreach questions
- Q01. I am curious about the Richter
scale. Some books tell me that each successive number increases
the power of an earthquake by a factor of 32, others say it
is 10. Which is it?
- This is a tricky question but we've come up with an answer
and two Web sites for you to look at. The short answer is, the
ENERGY of a quake goes up by a factor of 31.6 for each factor
of 1 on the Richter scale.
Both the USGS
site and the University
of Nevada site have detailed explanations of this scale
(and others).
Charles Richter developed the first 'scale' meant to quantify
the energy released by earthquakes. His work was done in the
Bay Area of California, and as such, is really only useful when
recording in this geologic domain. There are many factors that
influence the energy released and how the energy is felt, so
numerous scales are utilized now.One thing you should be aware
of is that scientists no longer use the Richter scale. Instead,
they use a number of different scales depending on what kind
of motion they are wanting to detect. The scale that is usually
reported to the public now is the Ml or Local
Magnitude — this is close enough to the old scale that
they don't bother to explain that it really isn't Richter any
more.
-
- Q02. When I look at a list of earthquakes,
I see that there are different letters after the magnitude.
What are they for?
- There are different ways of measuring magnitude and each way
is notated with its own abbreviation.
One thing you should be aware of is that scientists no longer
use the Richter scale. Instead, they use a number of different
scales depending on what kind of motion they are wanting to
detect. The scale that is usually reported to the public now
is the Ml or Local Magnitude — this is
close enough to the old scale that they don't bother to explain
that it really isn't Richter any more.
-
- Q03. Is the occurence of earthquakes
effected by the eruption of volcanoes?
- Learning about how earthquakes and volcanos are related is
a good project. A good place to look for information is:
http://vulcan.wr.usgs.gov/Outreach/framework.html.
Mt. St. Helens is an example where there were lots of earthquakes
before the eruption. See:
http://vulcan.wr.usgs.gov/Volcanoes/MSH/description_msh.html#msh_may18
-
- Q04. How do I get a job in Seismology?
- Some information about seismology as a career can be found
at:
http://www.seismosoc.org/education/careers.html
http://sep.stanford.edu/sep/jon/careeradvice.html
http://wwwsa.csuhayward.edu/~cdcweb/careers/physics.shtml
http://www.sciencecareersweb.net/GeolWeb/GeoCareer.htm
http://www.iris.edu/services/jobs.htm
GSN questions
- Q01. What stations are part of the GSN?
- Stations that function under the guise of the GSN are listed
here.
-
PASSCAL questions
PASSCAL has its own FAQ
page. |
