🏢 Base Isolation: fixed base vs. flexible isolators (2D)
Two identical buildings on the same shaking ground. The left one is bolted rigidly to its foundation. The right one rests on soft rubber-lead isolator bearings, which stretch the building's effective period so it barely feels the quake.
Peak ground accel: — g
Isolator period T: — s
Transmitted to fixed building: — g
Transmitted to isolated building: — g
Force reduction: —
Status: stable
fixed base (danger) base-isolated (safe)
Why it works: a base isolator lowers the building's natural frequency far below the earthquake's shaking frequency. Once the ratio of shaking frequency to isolator frequency climbs past ~√2, transmissibility drops well under 1 — the isolator absorbs the motion instead of passing it into the frame.
Drag the sliders — raise acceleration and match the isolator's resonant frequency to see it fail

Earthquake Base Isolation Simulator (2D)

This side-view simulator compares two identical buildings shaken by the same ground motion: one rigidly bolted to its foundation, the other resting on rubber-lead base isolator bearings. Adjust the ground acceleration, shaking frequency and isolator stiffness to see real base-isolation physics at work — lengthening a building's natural period pushes it out of resonance with the earthquake, cutting the force and acceleration that actually reach the structure.