SeedPSD EN FR
This service queries a database of power spectral densities (PSDs) calculated over one-hour segments. Individual daily PSDs are aggregated to show the probability distribution of seismic noise levels. PSDs are calculated with the method described by McNamara in 2004 using the PPSD class from ObsPy for a particular network/station/location/channel combination.
Usage
| Command | Description |
|---|---|
| /histogram | "Probability Density Functions" (PDFs) generation |
| /spectrogram | Spectrogram generation |
| /value | Extraction of PSDs values as text |
| /coverage | List of the periods for which PSDs are available |
How it works
The SeedPSD engine relies on the PPSD class from ObsPy. At both feeding and operation, any PPSD object is initialized using the default parameters as listed below.
| ppsd_length | 3600.0 |
|---|---|
| period_smoothing_width_octaves | 1.0 |
| period_step_octaves | 0.125 |
| period_limits | None |
| overlap | 0.5 |
Feeding
Metadata
When a StationXML metadata is submitted, the SeedPSD metadata ingestion engine:
- extracts each epoch from it using a FDSN Station webservice,
- extracts and stores in database the main values allowing to identify metadata changes (instrumental response, sampling rate, ...),
- compares the metadata already present in the database with the new ones before inserting them and, in case of discrepancy, invalidates any statistics calculated from them.
Data
When a MiniSEED data file is submitted, the SeedPSD data ingestion engine:
- checks the coverage and consistency of the metadata corresponding to the file,
- initializes a PPSD object from the content of the MiniSEED file,
- extracts and stores in database the main statistical values calculated by PPSD.
Operation
When a HTTP request is submitted, the SeedPSD exploitation engine:
- extracts the metadata for the target (NSLC) from the inventory,
- extracts from the database the statistical values corresponding to this target over the requested period (start/end),
- initializes a PPSD object from these values,
- uses this PPSD object to generate an image configured according to the options specified in the request parameters,
- sends the generated image to the client that made the request.