Observe this photo. It appears the shear walls in the unreinforced masonry structure survived, but the perforated front wall acting as a chord failed in this building. Meanwhile, the ceiling and roof diaphragms were adequately supported by the thicker shear walls, with minimal collectors on the front. Looks like the front wall was more brittle than the semi-rigid timber diaphragms and failed near its base, collapsing without bringing down the rest of the structure.
Also note the water tank / HVAC compressor on the light frame structure to the rear right, also would have experienced profound lateral forces due to the minimal support and sloshing anticipated, but it and the corresponding structure survived intact.
The upper photo is intriguing. Note the Soft story and out-of-plane vertical loading in the cantilevered deck adjacent to the fallen concrete structure. That concrete structure obviosly under went tremendous lateral forces, such hat it fell off the structure below it without obviously collapsing the structure, yet, even the tank remained intact as it slid off its elevated foundation and overturned resting on the tree below.
Technically, the Response Modification Coefficient, R, may not decrease as one goes up in the structure height,...as appears to have been obeyed,..concrete structure probably had an R of 3-5, while the lower story had a light frame structure with an R of about 2.5. Meanwhile the System Overstrength, (Omega) and Deflection Amplitude Factors, (C) are not allowed to decrease as you go down, but by more recent codes must correspond to R. Concrete structure probably had a C of about 3-5, while the lower stories had a C of about 2 - 2.5.
Results are the deflections above were even greater than a normal story drift due to types of bldg systems used in combination. I suspect the anchorages of the concrete structure failed, perhaps a non-building structure, maybe a water tank, and it traveled off the roof.
The bldgs were built for seismic loadings, intentionally or not, as their columns and main shear walls remained sound, at least in these photos.
