Shaking Videos and Viewer Ratings

What the clips are

The Shaking videos are camera recordings of real earthquakes: security and doorbell cameras, dashcams, phones, and news footage. They come from anywhere in the world, not only the region Intensity Lab models, because the effects that define intensity look the same everywhere. Where a quake is inside our region, its clips appear on its event page beside the simulated animations, so recorded and simulated shaking can be compared.

Each clip is a segment of a published video: a start and an end time chosen by a reviewer around one shot of shaking. A news report with several shots becomes several segments. The video is embedded from YouTube and never copied or cut; the player is held inside the segment.

How clips are found and chosen

1. Earthquakes likely to have been filmed are selected from the USGS catalog: a PAGER alert of yellow or higher, a ShakeMap or Did You Feel It? intensity of 5 or more, or magnitude 5.5 and above on land.
2. Videos are found by search, in the local language and in English, using the cities USGS PAGER estimates were most strongly shaken, and by reading the channels of video-licensing agencies, which often post weeks later.
3. A reviewer watches each candidate and approves it only if the shaking itself is visible. Footage of the aftermath alone is rejected: it shows damage, not the shaking that caused it.
4. The reviewer marks the segments, checks which earthquake it is, and records who filmed it.

How a rating works

Our reviewer rates every clip with a short interview, and any visitor can answer the same questions beside the playing clip, one topic at a time. It is in the style of the USGS Did You Feel It? form. Each of the 11 topics first asks whether the clip shows it: people, hanging objects, things on shelves, windows, heavy furniture, building walls and ceilings, cars, water, trees, animals, and the ground, roads and bridges. Only for a topic the clip shows does the rater see what to look for. The levels are hidden while answering, so the rater reports what happens rather than aiming at a number.

A clip changes as it plays, so any answers can be given together. A lamp may hang still at first and swing a few seconds later; people may stand calmly and then run. Each list therefore starts with "No apparent effect", which can be ticked beside the effects seen at other moments. It records that the rater looked, and sets no level.

The level the answers indicate is the highest level among them, shown with every answer behind it, so a single high observation is visible as such. Intensity is assigned from observed effects, not impressions, so there is no separate estimate to give.

The answers use the wording of the scale on our MMI scale pages, and each takes the level of the scale statements it stands for. A few of those statements come from other published versions of the scale (the USGS summary table, Wood and Neumann's 1931 scale, and the New Zealand scale); they appear with their sources on the MMI scale pages. Swimming pools are counted with water in containers (VI). They need care: a pool resonates with slow, long-period shaking, so far from a large earthquake it can slosh hard where other shaking is light. A clip whose only strong effect is a sloshing pool may overstate the intensity.

Rating a clip yourself

The level shown with each clip is our reviewer's, with the effects behind it. Rating a clip yourself is a way to look closely and to learn the scale: you see the level your answers point to and the scale statements behind it. Your answers are not scored against the reviewer's or shown to other visitors. Two careful raters often differ by a level, because a clip rarely shows every effect and the step between neighbouring levels is small. We keep the answers, as the privacy page describes, and may later study how they compare with ShakeMap and Did You Feel It?

What a rating can and cannot tell you

• It is good to about one level. A clip shows a few effects, not all of them, and neighbouring levels differ by a step or two in their effects.
• It describes one camera at one place. The Modified Mercalli intensity of a community is assessed from many observations across a town; a clip is one of them.
• A camera shows what is in frame. A clip of a quiet kitchen says nothing about the street outside.
• Upper floors shake more than the ground, and a building can amplify or damp shaking, so a clip from the tenth floor may show a higher level than people felt in the street.
• It is not the USGS Did You Feel It? intensity, which comes from people's reports of what they felt, nor ShakeMap's, which is estimated from instruments and models. Comparing the three is part of the purpose.

Credit and removal

Every clip names the person who filmed it when that is known, the channel that published it, and any licensing agency that holds its rights. Intensity Lab does not own this footage. To ask for a clip to be removed, see copyright and removal requests.