Geospatial plate analysis

Geospatial Plate Analysis

Purpose

Load and process PB2002 tectonic plate data (boundaries and plate polygons) using GeoPandas, then perform spatial operations like point-in-polygon tests and boundary extraction.

Data Format

PB2002_plates.json

• GeoJSON FeatureCollection with plate polygons
• Properties: Code (e.g., "PA"), PlateName (e.g., "Pacific")
• Geometry: Polygon or MultiPolygon (lon/lat, EPSG:4326)
• The Pacific plate ("PA") is a MultiPolygon that crosses the antimeridian (±180°)

PB2002_boundaries.json

• GeoJSON FeatureCollection with plate boundary LineStrings
• Properties: PlateA, PlateB (two-letter plate codes), Name, Type
• To get all boundaries of a plate (e.g., "PA"), filter where PlateA == "PA" OR PlateB == "PA"

Earthquake GeoJSON (USGS format)

• Features with Point geometry: [longitude, latitude, depth]
• Properties include: mag, place, time (Unix ms), type
• Feature id field contains the earthquake ID

Workflow

1. Load data

import geopandas as gpd

plates = gpd.read_file("PB2002_plates.json")
boundaries = gpd.read_file("PB2002_boundaries.json")
earthquakes = gpd.read_file("earthquakes_2024.json")

All data loads in EPSG:4326 (WGS84 lon/lat).

2. Extract a specific plate polygon

pacific_plate = plates[plates["Code"] == "PA"]

3. Filter points inside a plate

Use a spatial join or within test:

quakes_in_plate = gpd.sjoin(earthquakes, pacific_plate, predicate="within")

4. Extract plate boundaries

Filter boundaries where the plate code appears in either PlateA or PlateB:

pa_boundaries = boundaries[
    (boundaries["PlateA"] == "PA") | (boundaries["PlateB"] == "PA")
]

Antimeridian Handling

The Pacific plate crosses the ±180° meridian. GeoPandas handles MultiPolygon geometries natively, so sjoin with predicate="within" works correctly for point-in-polygon tests as long as the plate polygon is properly defined (which PB2002 data is).

Key Libraries

• geopandas — spatial data frames, spatial joins
• shapely — geometry operations (union, distance, nearest_points)
• pyproj — CRS transformations