Sep 8, 2026Visualization

Beneath the Threshold

Explore one month of recorded earthquakes and see how changing the minimum magnitude or depth changes the map, daily count, and list of events.

Start here

A quick guide to this quest.

Earthquake maps depend on which recorded events are included. This project starts with 653 earthquakes of magnitude 4.5 or higher listed by the U.S. Geological Survey during one 30-day window. You can narrow that fixed snapshot and see how the same filter changes every view.

Raise the minimum to M5.0
The event count drops sharply. Notice that the map looks quieter even though the underlying 30-day period has not changed.
Compare depths
Choose shallow, mid-depth, or deep earthquakes to see where those events appear and how their magnitudes are distributed.
Select a day
Choose a bar in the daily chart to filter the map, depth plot, and event list to that one UTC date.

Magnitude: A logarithmic measure of an earthquake's size. A small numerical increase represents a much larger physical event.
Minimum magnitude: The smallest earthquake included in the current view; events below the selected value are hidden.
Depth: How far below Earth's surface the earthquake began, measured in kilometers.
Catalog: The list of earthquake records in this fixed 30-day USGS snapshot, not a forecast or a complete measure of local danger.

U.S. Geological Survey · One 30-day snapshot

See how a filter
changes the map.

This project starts with 653 recorded earthquakes of magnitude 4.5 or higher. Raise the minimum to 5.0 first: the same month will suddenly look much quieter in every view.

Minimum magnitude shownM4.5M4.5M7.5

Limit the view by depth

Earthquakes shown653100% of the original 653 records

Typical depth10 kmThe median depth in the current view

Largest magnitudeM7.8Across the full 30-day window

Step 1 · Look at location

Where the listed earthquakes occurred

Shallow Mid-depth Deep

Each circle is one earthquake. Its position shows longitude and latitude, its size reflects magnitude, and its color shows depth. Change a filter above and this map updates.

This is a simple longitude-and-latitude plot, not a geographic risk map. It does not show population, buildings, fault exposure, or expected damage.

Step 2 · Look at time

How many events were listed each day

Taller bars mean more earthquakes matched your magnitude and depth settings on that UTC date. Select a bar to filter every other view to one day.

The first and last UTC dates cover only part of a day. A tall bar can reflect a related earthquake sequence, reporting changes, or both; it does not predict what comes next.

Step 3 · Compare size and depth

Magnitude versus depth

Depth increases downward to 700 km

Move right for a larger magnitude and down for a deeper earthquake. The background bands match the shallow, mid-depth, and deep filters above.

The chart stops at 700 km deep. USGS records can use different magnitude-calculation methods, so very close decimal values are not always directly comparable.

Step 4 · Inspect individual records

Largest events in this view

Select an event to bring its location, magnitude, depth, and recorded time into focus across the charts.

Selected recordM7.8

64 km NNW of Ende, Indonesia

10 km deep · Aug 14, 9:58 PM UTC

Why this exists

The question.

An earthquake map can look dramatically different depending on which events are included. Letting visitors change the minimum magnitude makes that filtering effect easier to understand while keeping depth and time visible.

How to begin.

Raise the minimum magnitude to M5.0 and watch every view update.

Method and limits

How the project was built.

I captured the official USGS feed of magnitude 4.5 and higher earthquakes at 15:37 UTC on September 8, 2026. For each record, I kept its location, magnitude, depth, time, place name, and identifier. Every filter and summary uses that saved snapshot, so the page does not change as the live feed changes. The source may use different methods to calculate magnitude, the first and last UTC dates cover only part of a day, and groups of nearby events may belong to the same earthquake sequence. The project therefore describes this list without making claims about causes, local danger, or future earthquakes.

What this demonstrates

Data analysis
Statistical reasoning
Visualization
Information design
Interaction design
Accessibility
Performance

Takeaways

In this saved 30-day snapshot, raising the minimum magnitude from 4.5 to 5.0 reduces the number of visible earthquakes from 653 to 192—a 71% drop. The map looks much quieter even though the time period has not changed.
Depth and day-by-day counts add useful context, but one month of magnitude 4.5 and higher earthquakes cannot measure local risk, establish a long-term pattern, or predict the next earthquake.

Sources

U.S. Geological Survey · U.S. public domain; attribution requestedM4.5+ Earthquakes, Past 30 Days — GeoJSON feed ↗