Frequently Asked Questions

Questions

Data

• What does the M, D, R, or Q character mean in my data file name?
• I downloaded some PASSCAL SEG-Y data. What do I do with it?
• I downloaded data in SAC format. Is the unit of dependent variable in the data mm/sec, or nm/sec, or mm/sec/sec, etc.?
• How do I get data out of a miniSEED volume?
• 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?
• 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?
• I only want data from stations that are a certain distance from an event. How do I do that?
• I need to know which stations were recording data during a specific event. How do I do that?
• What is the difference between assembled and customized data?
• How do I get station response information?
• How do I tell what data are available from the DMC?
• How do I request restricted data?
• Why are some data restricted from open access?
• In what format are the data at the DMC stored?
• What type of data is handled by IRIS?
• From what sources does the DMC get its data?

Data Management System

• Who runs the Data Management System (DMS)?

Education and Outreach

• FAQ from IRIS Reddit AskScience AMA
• How big must an earthquake be in order to be detected on the other side of the Earth?
• Following a major earthquake, can more large earthquakes be expected?
• Why did the magnitude of a recent major earthquake in the Pacific change from the initial reports?
• How do I get a job in seismology?
• Is the occurrence of earthquakes affected by the eruption of volcanoes?
• In a listing of earthquakes, what do the different letters after the magnitude mean?
• What does the Richter scale tell us about energy released by an earthquake?

Alaska

• How many earthquakes does Alaska experience in 1 year?
• Do all of Alaska’s earthquake occur on mapped faults?
• What parts of Alaska have the highest seismic hazards?
• Why are there so many earthquakes in Alaska that don’t occur at plate boundaries?
• Can a tsunami generated in Alaska affect Hawai’i?

Basin and Range

• How much does the Basin and Range Province expand each year?
• How does the thickness of the tectonics plate under the Basin and Range Province compare to other parts of the world?
• Why are there a large number of mines in the Basin and Range Province?
• Will any new volcanoes form in this region?
• How do volcanoes form in the middle of a tectonic plate?
• What role does the thickness of the tectonic plate in the Basin and Range Province play in the formation of volcanoes?
• Are any Basin and Range volcanoes active today?
• What types of volcanoes are found in the Basin and Range Province?
• What is the maximum depth of an earthquake in the Basin and Range Province?
• Why do earthquakes in the Basin and Range create fault scarps?
• How does a fault scarp form?
• How many earthquakes have occurred in the Basin and Range Province since 1872?
• Where is most of the stretching, or strain, happening in the western US?
• Do you see a pattern in the way the Basin and Range Province scientific GPS stations are moving? How would you describe it?

Cascadia

• What caused the Coast Range mountains?
• What caused the Cascade Range volcanoes?
• What caused the huge valley between the Cascade Range and the Coast Range?
• Why are there no volcanoes along the coast where the two colliding plates meet?
• What geologic features are directly caused by the subducting Juan de Fuca plate?
• Why are the volcanoes in the Pacific Northwest not located along the coast where the oceanic plate first goes under the continental plate?
• Why are the volcanoes of the Pacific Northwest in a line, rather than spread all over the place?
• What was the location of the largest known earthquake in the lower 48 states?
• Where does episodic tremor and slip occur?
• What causes episodic tremor and slip in subduction zones?
• Why is episodic tremor and slip so interesting?

Seismology and Earthquakes

• What is a plate boundary?
• Why do tectonic plates move?
• Are any of the states in the US free of earthquake hazard?
• How can earthquakes occur in the middle of a tectonic plate?
• What is seismic intensity?
• How do we estimate earthquake magnitude from intensity measurements for older earthquakes that were not recorded with seismic instruments?
• What is a seismic hazards map?
• How does the local geology affect seismic hazard maps?
• What do earthquakes have in common with x-rays?
• Why don’t scientists use X-rays to look inside of the earth?
• How do seismic waves make an image of the interior of the earth?
• How does a dense array of seismometers improve scientific results?
• What is seismic tomography?
• In the seismic tomography images why are there red colors under the Southwestern US and blue colors under the eastern US?
• How can someone be helped by an earthquake early warning system?
• Which is better to give earthquake early warning: seismometers or GPS?
• What should I do during an earthquake?
• Can a seismometer record you walking near a seismic station?
• Can explosions be recorded on seismometers?
• What is paleoseismology?
• What is a lahar?
• What is radiocarbon dating?
• What is liquefaction?
• What factors are necessary for liquefaction to occur?
• What cities are at risk for liquefaction damage?
• What is seismic retrofitting?
• What is a hot spot?
• What is the difference between a strike-slip fault and a reverse fault?

Tsunamis

• What does the word tsunami mean?
• What source causes the most widespread tsunamis?
• Why are there so many tsunamis in countries around the Pacific Ocean?
• When will the next tsunami from an earthquake in the Juan de Fuca subduction zone occur?
• Will people get warning before a tsunami?

General IRIS Questions

• How does my institution become a member of IRIS?
• Who is allowed to join IRIS?

GSN

• What stations are part of the GSN?

IRIS Supported Software

• Does IRIS have software tutorials?
• I am downloading a file through ftp that has ".tar," ".tar.gz," or ".tgz" in the filename. What does this mean and what do I do with it?
• How do I know if I'm running the latest version of software?
• When I try to run rdseed, I get an error message. What do I do?

PASSCAL and Instrumentation

• Where can I find information on PASSCAL?

Request Methods

• 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?
• What is a location identifier (or location code)?
• When making a BREQ_FAST request, do I have to include a network code?
• How do I know which request tool to use?