Streams and Traces#
For the purposes of the GMP format, we require that the traces be grouped into streams for which their corresponding properties (i.e., metadata) are consistent. Since a station may include traces from different locations or with different sample rates, a single station feature may contain multiple streams. The GMP format requires a “streams” key for each station dictionary. The streams key gives a list of dictionaries, and each dictionary represents a unique stream at that station.
Each stream dictionary contains the following keys:
- properties
an element to store stream-level metadata that contains the following keys (dictionary; required):
- band_code
The SEED band code (string; required).
- instrument_code
The SEED instrument code (string; required).
- samples_per_second
The number of samples per second of the time series (Hz) (float; required)*.
- stream_housing
A dictionary with the following keys (dictionary; required):
- cosmos_code
The COSMOS station type code (integer; required).
- description
The description associated with the cosmos_code (string; required).
- stream_depth
Depth (in m) of the stream relative to the ground surface (float; required).
- stream_location
Description of stream locaiton; especially useful for structures (e.g., “8th floor center” or “east wall”). Equivalent to COSMOS text header line 9, named “location” (string, optional).
- traces
A list of dictionaris in which each list element corresponds to a different trace (list; required).
It is important to note that since the “properties” element is a key within the stream dictionary, all of these traces must share the specified metadata. Traces can be either “as recorded” or derived traces. “As recorded” traces are the direct output of a data logger.
Derived traces are a function of the “as recorded” traces. Examples of
“as recorded” traces are BHN.-- and HNZ.01. Examples of derived traces
include:
The “greater of two horizontal” traces,
Transverse/radial traces, and
“RotD50” (see Boore 2010 for the full definition of RotD50).
An example stream dictionary structure is illustrated below.
{
...
"features": [
{
"type": "Feature",
"properties": {
...
"streams": [
{
"properties": {
"band_code": "H",
"instrument_code": "N",
"samples_per_second": 100.0,
"stream_housing": {
"cosmos_code": 10,
"description": "Building",
"stream_depth": 0.0
}
},
"traces": [
{
...
},
...
]
}
]
}
}
]
}
Each of the “traces” dictionaries must have the following keys:
- properties
A dictionary with the following keys (dictionary, required):
- channel_code:
SEED channel code (string, required).
- location_code
SEED location code (string, required).
- as_recorded
True if trace is a record from a data logger, False if trace is a function of multiple traces (bool; required).
- azimuth
Degrees clockwise from north of the trace orientation (float; required).
- dip
Degrees from horizontal of trace orientation (float; required).
- start_time
Trace start time; UTC ISO 8601 time format (string; required).
- end_time
Trace end time; UTC ISO 8601 time format (string; required).
- metrics
A list of dictionaries (dictionary; required).
An example trace dictionary structure is illustrated below.
{
...
"features": [
{
...
"properties": {
...
"streams": [
{
...
"traces": [
{
"properties": {
"channel_code": "HNE",
"location_code": "--",
"as_recorded": true,
"azimuth": 0,
"dip": -90.0,
"start_time": "2019-07-06T03:19:53Z",
"end_time": "2019-07-06T04:59:53Z"
},
"metrics": [
{
...
},
...
]
}
]
}
]
}
}
]
}