I’ve been in two different 6.9s and didn’t find them particularly alarming. Even brick buildings held up, though some facade was lost.
The big gaps in the road must have had contributing factors...erosion etc.
And this quake is finally pegged at 7.0 right?
You can just continue on being you....
How “big” or “huge” the effects of a 7.0 are is depends on more than just the original energy released. Depth of the quake has already been mentioned, and duration also counts. Other major factors are how efficiently the shock waves are transmitted (the largest of the New Madrid quakes in 1811-1812 reputedly rang church bells in New England!), and whether the soil(s) liquify (which was also devastating in the New Madrid quakes.) The New Madrid quakes of 1811-12 were much larger, of course, but even a 7.0 there any time in the near future could largely destroy some of the nearby towns.
The magnitude scale is really comparing amplitudes of waves on a seismogram, not the STRENGTH (energy) of the quakes. So, a magnitude 8.7 is 794 times bigger than a 5.8 quake as measured on seismograms, but the 8.7 quake is about 23,000 times STRONGER than the 5.8!
Since it is really the energy or strength that knocks down buildings, this is really the more important comparison. This means that it would take about 23,000 quakes of magnitude 5.8 to equal the energy released by one magnitude 8.7 event. Here's how we get that number: One whole unit of magnitude represents approximately 32 times (actually 10**1.5 times) the energy, based on a long-standing empirical formula that says log(E) is proportional to 1.5M, where E is energy and M is magnitude. This means that a change of 0.1 in magnitude is about 1.4 times the energy release. Therefore, using the shortcut shown earlier for the amplitude calculation, the energy is,
32 * 32 * 32 / 1.4 = 23,405 or about 23,000
So, a 7.0 is significantly stronger than a 6.9 - 40% stronger. The San Fran earthquake of 1989 was a 6.9 and it brought down freeways.
Erosion? Don't think so.
The whole area is a basin full of deep wet soil. Soil liquefaction occurs even in a moderate earthquake and is incredibly damaging. Every unsupported slope turns into a mudslide. Anything solid atop the soil is tossed by waves of soil and will be subject to tilting, capsizing, sinking, or just breaking up from tensile stress across unsupported sections. For example most roads are build on fill which in turn distributes the load across a wider area of soil, but has no serious tensile strength. When the supporting soil moves, the fill pad can break up.