TREMR

Tremr is a free, real-time global earthquake monitor. Our goal is simple: make seismic data from around the world immediately accessible and understandable to everyone — whether you're a curious reader, a researcher, or someone who just felt their building shake.

Every feature on Tremr is designed to surface the information that matters most, as quickly as possible, with no account required, no app to install, and no cost to the user.

How We Source the Data

All earthquake data displayed on Tremr comes directly from the United States Geological Survey (USGS) Earthquake Hazards Program — the most comprehensive and authoritative real-time seismic monitoring network in the world. The USGS operates over 2,000 seismograph stations globally and publishes earthquake data within minutes of detection.

We query the USGS GeoJSON feed at regular intervals (every five minutes) and display the results with no modification to the underlying data. This means every magnitude, location, depth, and timestamp shown on Tremr comes directly from USGS scientists and their global sensor network. When you filter by time range — past hour, past 24 hours, past 7 days, or past 30 days — we request the corresponding USGS feed to keep data volumes manageable and load times fast.

Each earthquake in the feed includes: magnitude (Mw), geographic coordinates, focal depth, origin time in UTC, a human-readable place name, and tsunami alert status where applicable. Tremr surfaces all of this in the event list, the interactive map, and the detailed event panel.

Understanding Earthquake Magnitudes

Earthquake magnitude is measured on the Moment Magnitude scale (Mw), which replaced the older Richter scale in scientific use. Unlike the Richter scale — which was designed for local California earthquakes measured on a specific instrument — Moment Magnitude works consistently for earthquakes of all sizes, anywhere in the world.

The scale is logarithmic: each whole number increase represents approximately 31.6 times more energy released. A magnitude 6.0 earthquake releases roughly 1,000 times more energy than a magnitude 4.0 earthquake. Tremr uses the following classification system, which mirrors standard seismological practice:

Range	Class	Typical Effects
M0 – M1	Micro	Not felt. Detected only by instruments.
M1 – M2	Minor	Rarely felt. Recorded on local seismographs.
M2 – M3	Light	Often felt indoors. Rarely causes damage.
M3 – M4	Moderate	Widely felt. Minor damage possible near epicentre.
M4 – M5	Strong	Felt by many. Objects may fall. Significant damage to weak structures.
M5 – M6	Major	Felt broadly. Moderate to heavy damage in populated areas.
M6+	Great	Severe destruction possible. Can be felt hundreds of kilometres away.

Depth is equally important when interpreting an earthquake's impact. Shallow earthquakes (0–70 km depth) typically cause more surface damage than deep ones because the seismic waves have less material to travel through before reaching the surface. Deep-focus earthquakes (below 300 km) can still be detected across vast distances but rarely cause significant surface damage.

The Science of Seismic Activity

Earthquakes occur when stress accumulated along geological faults is suddenly released, sending seismic waves radiating outward in all directions. The vast majority of earthquakes happen along tectonic plate boundaries — the edges where the Earth's crustal plates meet, grind past one another, collide, or are pulled apart. The Pacific "Ring of Fire," which encircles the Pacific Ocean, accounts for roughly 90% of the world's seismic activity and is visible on Tremr's map as a near-constant ring of earthquake dots.

Three primary fault types drive most earthquakes:

• Strike-slip faults — plates slide horizontally past each other, like the San Andreas Fault in California.
• Thrust (reverse) faults — one plate is pushed up and over another, responsible for many of the world's largest earthquakes including the 2011 Tōhoku event.
• Normal faults — plates pull apart, common in continental rift zones.

Seismic waves come in two main types: P-waves (primary or compressional waves), which travel fastest and are the first to arrive at a seismograph, and S-waves (shear or secondary waves), which travel slower but carry more destructive energy. The time difference between P and S wave arrivals at multiple stations allows seismologists to pinpoint the earthquake's location and depth with high precision.

Aftershocks — smaller earthquakes that follow a main event — occur as the surrounding crust adjusts to the stress change. A significant earthquake can produce aftershocks for days, weeks, or months. Tremr's live feed will show aftershock sequences in real time as they are recorded by USGS sensors.

Tsunami Alerts

Undersea earthquakes above approximately M7.0 in shallow coastal regions can displace large volumes of water, generating tsunamis. Tremr flags any event marked with a tsunami alert by USGS with an alert indicator in the event detail panel. These alerts originate from the USGS data feed and reflect advisories issued by the NOAA Pacific Tsunami Warning Center and regional tsunami warning systems. Always follow guidance from local emergency authorities if you are in a coastal area during a significant offshore earthquake.

How to Prepare for Seismic Activity

If you live in or travel to a seismically active region, a few basic preparations can make a significant difference:

• Know your risk. Use Tremr's filter and "Near Me" feature to understand how frequently earthquakes occur in your area and what magnitudes are typical.
• Secure your space. Strap tall furniture (bookshelves, water heaters) to walls. Store heavy items on low shelves. Know where gas and water shut-offs are located.
• Prepare a kit. Keep at least 72 hours of water (4 litres per person per day), non-perishable food, a first-aid kit, a flashlight, and copies of important documents in an accessible location.
• Make a plan. Establish a family meeting point and an out-of-area contact. Practice "Drop, Cover, and Hold On" — drop to hands and knees, take cover under a sturdy desk or against an interior wall away from windows, and hold on until shaking stops.
• After shaking stops. Check for gas leaks, downed power lines, and structural damage before re-entering any building. Expect aftershocks and be prepared to take cover again.

For region-specific guidance, consult your national or local emergency management agency. In the United States, ready.gov and the USGS Earthquake Hazards Program are authoritative sources.