# Data dictionary: one week of earthquake catalog records

This dictionary covers the columns used in the accompanying Data Story. The frozen `earthquakes.csv` keeps the full USGS API export. A row represents **one cataloged earthquake event**. There are 155 rows, all with a distinct `id`, for August 1–7, 2026 UTC, with reported magnitude at least 4.5. Downloaded September 25, 2026. Source: [USGS Comprehensive Earthquake Catalog](https://earthquake.usgs.gov/data/comcat/) and [FDSN event API](https://earthquake.usgs.gov/fdsnws/event/1/1). The `data-dictionary.md` wording is a teaching simplification; consult USGS documentation for scientific analysis.

| Field | Meaning | Unit / format | How this lesson uses it |
| --- | --- | --- | --- |
| `id` | Catalog event identifier | Text | Confirm that the selected rows are distinct events. |
| `time` | Estimated time of event origin | ISO 8601 UTC, e.g. `2026-08-01T00:39:22.320Z` | Use the first ten characters for the UTC calendar date. A local date could differ. |
| `mag` | Reported magnitude value | Number | The original query keeps values >= 4.5; students repeat counts for values >= 5.0. Magnitude is not a direct damage measure. |
| `magType` | Method used for the reported magnitude | Text, such as `mb` or `mww` | Shows that the export mixes magnitude methods; the lesson does not compare or convert them. |
| `depth` | Estimated depth below the surface | Kilometers | Optional mean/median comparison. A depth summary does not establish hazard. |
| `place` | Human-readable location label | Text | Helps interpret a sample row; it is not a precise geographic boundary. |
| `status` | USGS review status in this snapshot | Text (`reviewed`) | All 155 rows are reviewed as saved; that does not imply completeness or immutability. |
| `type` | USGS event type | Text (`earthquake`) | Confirms the snapshot's 155 rows are labeled earthquakes. |

The catalog is selective: minimum magnitude 4.5, one week, global scope, and whatever the catalog contained when downloaded. Smaller events can be missing, and event values can later change. The dataset cannot by itself establish a long-term trend or local risk. The file's SHA-256 is `6493902079340c728403aa09928826a377dbfb040f78ad51d60f2ad30a7b0acb`.

To reproduce the selection, use the FDSN event API with `format=csv&starttime=2026-08-01&endtime=2026-08-08&minmagnitude=4.5&orderby=time-asc`. A fresh query may return revised records; the bundled CSV is the fixed classroom snapshot.

Prepared by JR, founder of [Telemetry](https://telemetry.sh/), with AI assistance. Untested teaching draft. USGS has not endorsed it. No account or student data is required.