Understanding Earthquakes
Earthquakes are sudden ground vibrations caused by the movement of tectonic plates beneath Earth's surface. Our planet's outer shell is divided into large plates that float on the semi-fluid mantle below. When these plates interact at their boundaries—colliding, pulling apart, or sliding past each other—the resulting stress can release enormous energy in the form of seismic waves.
Monitoring earthquakes is critical for public safety, scientific research, and disaster preparedness. Modern seismograph networks detect thousands of seismic events daily around the globe, most too small to feel. Significant earthquakes, however, can cause devastating damage and loss of life, making real-time monitoring essential for early warning systems.
ShakeViewer provides an accessible way to visualize this constant seismic activity, aggregating data from the world's leading seismological agencies into a single interactive map interface.
How the Earthquake Magnitude Scale Works
Earthquake magnitude measures the energy released at the source of the quake. While the original Richter scale introduced magnitude measurement in 1935, modern seismology primarily uses the moment magnitude scale (Mw), which is more accurate for large events. The scale is logarithmic: each whole-number increase represents approximately 32 times more energy released.
ShakeViewer uses a color-coded system to represent magnitude categories at a glance:
- Green (below 3.5) — Minor: Generally not felt by most people, but recorded by instruments.
- Yellow (3.5–4.5) — Moderate: Often felt, rarely causes damage. Objects may rattle indoors.
- Orange (4.5–6.0) — Strong: Can cause damage to poorly constructed buildings. Widely felt across the region.
- Red (above 6.0) — Major: Potentially destructive over a large area. These events are highlighted with pulsing markers on the map.
Real-Time Earthquake Monitoring
ShakeViewer aggregates seismic data from two primary sources: the United States Geological Survey (USGS) and the European-Mediterranean Seismological Centre (EMSC). The application automatically refreshes data every 90 seconds, ensuring near-real-time monitoring.
The interactive map displays earthquake markers sized by magnitude, with color coding for severity. Users can switch between day, week, and month views, filter by depth category, set minimum magnitude thresholds, and overlay tectonic plate boundaries. The Custom Search mode allows historical queries with custom date ranges, magnitude thresholds, and geographic bounding boxes drawn directly on the map.
"Felt reports" (available for USGS data) indicate how many people submitted reports of feeling the earthquake, providing valuable ground-truth data about how widely an event was perceived.
Earthquake Safety Tips
During an earthquake — Drop, Cover, Hold On:
- Drop to your hands and knees to prevent being knocked down.
- Cover your head and neck under a sturdy desk or table. If no shelter is nearby, crouch near an interior wall.
- Hold On to your shelter until the shaking stops.
Be prepared: Maintain an emergency kit with water, food, first-aid supplies, a flashlight, and batteries. Identify safe spots in each room and practice earthquake drills. After an earthquake, move cautiously, check for injuries and structural damage, and be prepared for aftershocks.
Frequently Asked Questions
- How often is the earthquake data updated?
- ShakeViewer refreshes earthquake data every 90 seconds from both USGS and EMSC sources, providing near-real-time monitoring of seismic activity worldwide.
- What does earthquake magnitude mean?
- Magnitude measures the energy released during a seismic event on a logarithmic scale. Each whole number increase represents roughly 32 times more energy. ShakeViewer displays earthquakes of magnitude 2.5 and above.
- What is the difference between earthquake depth categories?
- Shallow earthquakes (less than 70 km) typically cause the most surface damage. Intermediate earthquakes (70–300 km) produce less surface shaking, while deep earthquakes (over 300 km) are rarely felt on the surface.
- Where do most earthquakes occur?
- Most earthquakes occur along tectonic plate boundaries, especially around the Pacific Ring of Fire. ShakeViewer can display tectonic plate boundary overlays to help visualize this pattern.
- What are tectonic plate boundaries?
- Tectonic plate boundaries are zones where Earth's lithospheric plates meet. Divergent boundaries (plates moving apart), convergent boundaries (plates colliding), and transform boundaries (plates sliding past each other) are the three main types. Most earthquakes and volcanoes are concentrated near these boundaries.
- How can I search for historical earthquakes?
- Use ShakeViewer's Custom search mode to set a specific date range, minimum magnitude, and optionally draw a geographic bounding box on the map. The system queries both USGS and EMSC databases for matching historical events.