function toGeoJSON(data) {
const features = data.map((d) => ({
type: "feature",
geometry: {
type: "Point",
coordinates: [d.lon, d.lat]
},
properties: {
area_id: d.area_id,
depth: d.depth,
time: d.begperiod,
activity: d.activity
}
}));
return { type: "FeatureCollection", features: features };
}