Fetching site table

📍 Fetching Site Table

This step in the NZGMDB pipeline collects metadata for all seismic stations within New Zealand. It combines station information from GeoNet with local metadata and assigns each site to a basin if applicable.

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🚀 Entry Point

To generate the site table, run the following Python script:

python -m nzgmdb.scripts.run_nzgmdb generate-site-table-basin <main_dir>

• <main_dir> is the top-level output directory where NZGMDB stores its results.

Example:

python -m nzgmdb.scripts.run_nzgmdb generate-site-table-basin nzgmdb_output/

This will create the file:

nzgmdb_output/flatfiles/site_table_basin.csv

⚙️ Process

🔹 Fetch Station Metadata

• Uses ObsPy’s FDSN client to download station metadata from the GeoNet network, including:
  • Network code
  • Station code
  • Latitude / Longitude
  • Elevation

🔹 Merge with Local Site Metadata

• The fetched station list is merged with a local Geonet metadata summary CSV, which includes geotechnical properties such as:
  • NZS1170 Site Class
  • Vs30 median and standard deviation
  • Basin depths (Z1.0, Z2.5)
  • Other site parameters like T0 and Q factors
• ⚠️ Note: This metadata is loaded from the NZGMDB data registry and is not found directly from the GitHub repository.
• Stations missing from the metadata summary may have missing fields after the merge. These are handled later in the quality db step to filter these out and report which sites have missing data but have quality waveforms.

🔹 Assign Tectonic Domain

• Each site is assigned a tectonic domain number by spatially intersecting the site coordinates with a tectonic domain shapefile:
  • TectonicDomains_Feb2021_8_NZTM.shp (and associated .dbf, .shx files)
• The output field site_domain_no represents the tectonic domain ID indicating the regional tectonic environment of the station.

🔹 Add Basin Information

Adds basin information to the site table dataframe by checking if station coordinates fall inside known basin polygons.

• Loads the latest version of basin outlines from the velocity modelling repository.
• Uses a spatial point-in-polygon test to assign the basin name to sites located within basin boundaries.
• Adds a new column basin to the input dataframe.

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📦 Output

• The final merged dataframe gets saved as site_table.csv in the flatfiles directory containing:

Column	Description
net	Network code (e.g., "NZ")
sta	Station code identifier (e.g., "DCZ")
lat	Latitude of station location (WGS84)
lon	Longitude of station location (WGS84)
elev	Station elevation in metres
site_class	NZS1170 site classification (A is best, D is worst)
Vs30	Shear wave velocity (Vs30) value in m/s
Vs30_std	Standard deviation of Vs30
Q_Vs30	Quality flag for Vs30
Vs30_Ref	Reference for Vs30 data source
T0	Fundamental site period
T0_std	Standard deviation of T0
Q_T0	Quality flag for T0
D_T0	Data Source for T0
T0_ref	Reference for T0 data source
Z1.0	Basin depth to 1.0 km/s shear wave velocity (metres)
Z1.0_std	Standard deviation of Z1.0
Q_Z1.0	Quality flag for Z1.0
Z1.0_ref	Reference for Z1.0 data source
Z2.5	Basin depth to 2.5 km/s shear wave velocity (metres, scaled)
Z2.5_std	Standard deviation of Z2.5
Q_Z2.5	Quality flag for Z2.5
Z2.5_ref	Reference for Z2.5 data source
site_domain_no	Integer tectonic domain ID assigned from shapefile
basin	Basin name assigned based on spatial polygon test

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🔗 Related Steps

• Next: Parse GeoNet - Parses GeoNet data to extract waveform files and metadata