Station Metadata: What do I Need? Dr. Mary Templeton IRIS Data Management Center Managing Data from Seismic Networks August 20-26, 2017 Pretoria, South Africa

Why is Metadata Important? To use data, you need to know where and how it was recorded: x,y,z,t How do you translate the time series to ground motion? Direction of motion recorded Amplitude scaling Phase shifting The data format must be understood Metadata is easiest to record before it’s forgotten

Steps for Building Metadata Register your network and station names Networks: http://www.fdsn.org/networks/request/ You now have the ability to provide or request the FDSN creates a Digital Object Identifier (DOI) for you network Stations: http://www.isc.ac.uk/registries/registration/ Create a dataless SEED volume Enter network information Enter information for a single station Optional: Add additional stations using the first as a “clone”

What do I Need? Example: II.SUR.00.BH{12Z} Network information FDSN network code (network ID) Operating institution (network operator) Blue terms are those used by PDCC Build A Station

What do I Need? Station information Registered station code (station name) Station long name (site description) Location of the station and it’s sensors Latitude (degrees from -90 to +90) Longitude (degrees from -180 to +180) Elevation (ground surface and sensor in m) Depth (surface elevation – sensor elevation in m)

What do I Need? Station information Sensor wiring convention Normal: upward ground motion produces a positive Z amplitude; Z dip is -90 (most earthquake sensors) Reverse: upward ground motion produces a negative Z amplitude; Z dip is +90 (industry geophones) Sensor channel orientations Angle from magnetic north to each horizontal channel (azimuth in degrees from 0 to 360)

What do I Need? Station information Sample rate 20 Sensor long-period corner 360 s (STS-1) Sensor gain 2400 V/m/s (STS-1 nominal gain) No corner period needed for accelerometers

What do I Need? B,H,C,F S,E,D,G H L BH? (40 sps) SH? (40 sps) SL? (40 sps) Is the nominal sensor gain larger or smaller than 200 V/m/s? How channel naming depends on sensor corner frequency and gain

What do I Need? Station information Instrument response Sensor Sensitivity Poles and zeros A0 normalization factor Datalogger Preamplifier gain Bit weight (A/D scale factor) FIR coefficients for your field acquisition settings other Other – information about other acquisition settings that affect response (e.g. optional filters)

OR If your instruments are in the Nominal Response Library… http://ds NRL has a web version and is available to PDCC Selecting correct response depends on knowing the characteristics and acquisition parameters for your instrumentation

…you will need Station information Instrument response Sensor Manufacturer Model Other Other – sometimes corner period, sensitivity, component

…you will need Station information Instrument response Datalogger Manufacturer Model Preamplifier gain Sample rate Other Other – linear vs. nonlinear FIR filters, software gain settings, optional IIR filters…

What do I Need? Station information Optional Text description of instrumentation Instrument serial numbers Comments documenting timing and other data problems

What do I Need? And Finally…. Time span (epoch) for which this information is valid (YYYY,JJJ,HH:MM:SS.ffff) If any of this metadata changes, a new epoch needs to be created with updated metadata Epochs must not overlap in time - you must close the previous epoch (edit the end time) whenever you add a new epoch for the same channel.

After the Break… …we’ll use metadata for GSN station II.SUR (Sutherland, South Africa) to learn how to create a Dataless SEED volume using the program PDCC.