Beamforming Playgroundⁱ

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.

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?

The simplest approach: Just start with the first app (Plane Waves), and follow your curiosity! Each app has a "Guided Exercise" in the ☰ menu that walks you through specific tasks.

What you'll do in each app:

• Build arrays by clicking on the map, or choose real arrays like Gräfenberg (Germany) or NORSAR (Norway)
• Control wavefields using sliders for direction, velocity, and frequency
• Steer the beam by clicking in the array response plot—watch the beam trace change as you find the maximum
• Follow guided exercises via the ☰ menu for structured step-by-step learning

No installation needed. Everything runs in your browser. Best experienced on a desktop or laptop with a mouse.

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.

If you want to explore further: The apps are organized into "Basics" (for beginners) and "Advanced Concepts" (for those with some experience). You can jump around based on your interests!

What you'll learn in each app:

• Plane Waves: Array steering fundamentals, response patterns, resolution limits, side lobes
• Broadband Signals: Why wider frequency bands give cleaner beams
• Noisy Signals: How beamforming improves signal-to-noise ratio
• Multiple Sources: When can we separate two simultaneous arrivals?
• Matched Field Processing: Handling curved wavefronts from nearby sources
• Wave Types: Working with real earthquake wave types (P, S, Rayleigh)
• 3-Component Beamforming: Using multiple sensor orientations for polarization analysis

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.