Beamforming Playground

What is this website?

This is an interactive learning tool for seismic beamforming—a technique used by seismologists to detect earthquakes and understand how seismic waves propagate through the Earth. Think of it like a virtual laboratory where you can experiment with arrays of seismic sensors and see what happens.

No prior knowledge is required! You can start exploring immediately, and each app guides you through specific concepts step by step. The whole playground is free and open source, runs entirely in your browser, and works offline after your first visit.

Why should I care about beamforming?

Beamforming is fundamental to modern seismology. Here's why it matters:

• Earthquake detection: It helps find small earthquakes that would otherwise be lost in background noise
• Determining earthquake location: It tells us both where an earthquake happened and how the ground moved
• Understanding Earth's interior: By analyzing how waves travel through the Earth, we can map its internal structure
• Real-world applications: The same principles apply to radar, sonar, wireless communications, and even medical imaging

What is Beamforming, exactly?

Imagine standing in a field with your eyes closed, hearing a bird chirp. With one ear, you know something is making a sound. With both ears, you can tell which direction the sound is coming from—because sound reaches your ears at slightly different times.

Beamforming does the same thing, but with seismic stations instead of ears. By combining signals from multiple stations spread across tens or hundreds of kilometers, we can:

• Enhance weak signals (like distant earthquakes)
• Determine the direction waves are coming from
• Measure how fast waves are traveling (their velocity)
• Separate different types of waves arriving at the same time

The mathematical technique is called "beamforming" because we can mentally "point" our array in different directions—like steering a beam of light—to see where the strongest signal comes from.

What's the difference between seismology and other beamforming?

You might be familiar with beamforming from other fields (acoustics, antenna arrays, ultrasound). Seismic beamforming has some unique twists:

• 2D arrays: Most seismic arrays are spread across Earth's surface (2D), not in a line (1D)
• Slowness, not angle: We measure wave speed as "slowness" (inverse velocity) and steer in both azimuth and slowness
• Multiple wave types: Earthquakes generate P-waves, S-waves, and surface waves—all behave differently
• Plane waves from far away: For distant earthquakes, we assume flat wavefronts; for nearby sources, we need curved wavefronts (Matched Field Processing)

This website lets you explore all these concepts interactively, starting from the basics and progressing to more advanced topics.

How do I use this website?

On your first visit to each app, a short guided walkthrough appears and shows you the ropes. You can restart it anytime from the ☰ menu (Restart Walkthrough), or skip it and explore freely.

The core interactions are the same in every app:

• Click the map to place a station, drag a station to move it, and press & hold a station to bring up a red Delete pill
• Click the array-response plot to steer the beam — watch the traces react as you find the maximum
• Lock icons pin one parameter (velocity, wavelength, or frequency) so the others stay physically consistent (v = f · λ). The yellow slider track shows the allowed range
• Load real arrays — like Gräfenberg (Germany) or NORSAR (Norway) — from the ☰ menu

Every app also includes guided exercises: open the 📖 book icon next to the Array header and pick a topic — it unfolds right in the panel.

No installation needed — everything runs in your browser and works offline after the first visit. Works with mouse and touch; best on a desktop, laptop, or tablet.

Which app should I start with?

If you're new to beamforming: start with Plane Waves — it teaches the fundamentals: array response patterns, side lobes, resolution, and how to steer the beam. The landing page groups the apps into Fundamentals, Seismic Waves, and Advanced Techniques, roughly in increasing difficulty.

What you'll learn in each app:

• 1 · Plane Waves: array steering fundamentals, response patterns, resolution limits, side lobes
• 2 · Broadband Signals: why wider frequency bands give sharper peaks and fewer side lobes
• 3 · Noisy Signals: how beamforming improves the signal-to-noise ratio
• 4 · Multiple Sources: when can we separate two simultaneous arrivals?
• 5 · Wave Types: how sensitive arrays are to P, S, Love, and Rayleigh waves
• 7 · 3-Component Beamforming: polarization and wave-type-specific beamforming with three-component sensors
• 8 · FK Analysis: how plane waves map into wavenumber–frequency space
• 9 · Matched Field Processing: handling curved wavefronts from nearby sources
• 11 · DAS Beamforming: fibre-optic cables as dense virtual arrays

How much math do I need to know?

Short answer: None! These apps are designed to build intuition first, without equations. You'll learn by doing—clicking, sliding, observing, and experimenting.

Longer answer: The underlying mathematics involves Fourier transforms, complex numbers, and wave propagation physics. But you don't need to understand the math to grasp the concepts. If you're curious, the code is all here for you to explore—it's written in plain JavaScript with no external dependencies.

I'm a teacher/instructor. How can I use this?

These apps work great for:

• Live demonstrations in lectures—project the screen and let students guide you
• Labs or problem sets—have students complete the guided exercises
• Self-paced learning—assign specific apps as homework
• Exploration—let curious students discover concepts on their own

Each app includes guided exercises that work well as structured activities. The apps complement (rather than replace) textbooks and lectures by making abstract concepts tangible. And since the site works offline once loaded, it's reliable even in lecture halls with poor Wi-Fi.