How Did Aftershock Activity Unfold After the Kumamoto Earthquake?

2026

Responsive chart embed

Copy the embed code and place this chart on your website.

High-Resolution Chart Images

Open the image in Google Drive to view or download.

View images

Usage Guidelines‍

You may use the embed code and chart images in articles, presentations, reports, educational materials, and social content.

Do not remove embedded credits, misrepresent the data, resell the materials, or redistribute the original files.

About This Chart

Data Visualization Method

Data: Earthquake events reported by the Japan Meteorological Agency (JMA) at seismic intensity 1 or above, each with an observed location, magnitude, and origin time.
Period and area: The 48 hours following the mainshock (2026-07-28 16:27 JST to 2026-07-30 16:27 JST), within a 100 km radius of the mainshock epicenter.
Selection: 280 reported events in total, including the mainshock (279 excluding it). The 100 km radius is a selection rule for this visualization, not a physical classification of which events are aftershocks.
Chart form: An animated map. Each earthquake plays back in the order it occurred and is drawn as a small fixed center point marking the reported coordinates, surrounded by concentric rings scaled to magnitude. Larger events receive more layers, so stronger earthquakes appear wider and more complex.

Creator's Note

The starting question for this chart was simple: can a single point on a map be made to feel like an earthquake, rather than a static dot? Plotting a location and a magnitude is easy; making it read as a tremor is the harder part.

Rather than a single circle per event, each earthquake was rebuilt from a center point and several overlapping pulse layers, brightest at the core and fading outward. The intent was to convey the intensity and timing of activity intuitively, not to rank or dramatize the event.

Data Sources

Japan Meteorological Agency (JMA) — primary source for event locations, magnitudes, and origin times.
USGS Event API — cross-check for the mainshock.

Limitations

The size of each circle is a relative visual value derived from magnitude. It does not represent the physical reach of seismic waves, the area of shaking intensity, or any damage radius. The multiple layers drawn for one earthquake are a single event rendered in overlapping parts, not separate earthquakes.

The dataset is limited to events JMA reported at intensity 1 or above, so it is not a complete instrumental catalog of every microearthquake in the window. The 100 km radius is a visualization boundary and does not confirm that every event within it is causally an aftershock of the mainshock.

Magnitudes differ by agency because measurement methods differ: JMA reported the mainshock as M7.1, while USGS reported M6.8. The 48-hour window is the scope of this visualization, not a statement that seismic activity ended at that point.