System Update Log
A plain-language summary of significant changes as we improve Intensity Lab. Minor fixes and behind-the-scenes work aren't listed here.
- The home page now opens with recent seismic activity rather than a button pointing at it: a map of the events from the past 30 days, sized by magnitude and coloured by the strongest intensity estimated at any populated place, beside a list of the most recent few. Grey means an event has been detected but has no intensity report yet. The introduction above it is shorter.
- For a while you will also see reports and animations for smaller earthquakes than usual — magnitude 4.0 and above, rather than the magnitude 5.5-ish events that normally shake hard enough to produce them. This is deliberate and temporary. The full chain from detection through intensity estimates, email and animation to video is hard to check when qualifying earthquakes are months apart, so we are letting smaller ones through to confirm every step works.
- Two things to know while that lasts. You may get email about shaking you did not feel — a magnitude 4.0 is usually intensity III or below where people are, which is weak or unnoticed. And the simulated ground motion behind these animations is below the magnitude range the SCEC Broadband Platform is calibrated for, so treat those videos as a test of the system rather than a statement about the earthquake.
- There is now a page explaining how Intensity Lab uses the BBP simulation service, at Technical Information → How We Use the BBP Simulation API. It follows one earthquake through the whole exchange: what USGS supplies about the fault, how the cities and distance points are chosen, how the simulation method and crustal model are picked, what the request actually contains, how site stiffness (Vs30) is resolved, and what comes back — acceleration seismograms that are integrated twice to drive the animations. Two diagrams and no equations.
- Intensity Lab and BBP Services are now operating together. Intensity Lab reports what the shaking was at populated places and turns it into media people can watch; BBP Services runs the physics-based ground motion simulations behind those animations. Splitting them means each does one job properly: the consumer site is not carrying a simulation platform, and the simulation platform publishes its own verification evidence rather than asking you to take the animations on trust.
- Everything the site produces after an earthquake is now described in one place, with a live example of each: the population and seismic station intensity lists, the nearest site report, and the three kinds of animation.
- The site now states plainly who builds it, where every number comes from, and what it should not be relied on for, across a rewritten About page and a disclaimer covering data sources, editorial standards and corrections.
- Shaking animations can now be driven by physics-based simulated ground motion rather than motion synthesized from a peak value. This is what lets us show the shaking at a town with no seismometer in it, which is most towns.