The ground's own motion

Near Giza the ground moves by hundredths of a micrometre per second on its own

The nearest open broadband record is MedNet station KEG at Kottamya, 67 km east of Khafre: an STS-1 seismometer in a 7 m vault on a limestone hill. Twelve days of 1996, one in the middle of each month, three components, instrument response removed, turned into power spectra the way network operators do. Its microseismsmicroseism seismicThe ground’s constant hum from ocean swell, strongest between 0.1 and 0.3 Hz, felt everywhere on Earth as surface waves kilometres long. are the region’s, Giza’s included; above 1 Hz a quiet hill is a lower bound for a plateau at the edge of a city of twenty million.

A quiet site: well above the global floor, far below the noisiest stations

At Kottamya, 67 km east of Giza, the median vertical ground velocity is 0.049 um/s in the microseism band (0.1-0.3 Hz) and 0.029 um/s by day, 0.028 um/s by night at 1-3 Hz (1996, twelve days, instrument response removed). Peterson's global models bound the microseism band between 0.02 and 3.5 um/s.

Giza’s ground rings near 0.6 Hz, and the Great Pyramid near 2.3 Hz

An ambient-noise survey of Khufu’s pyramid, 37 points in its chambers, on its blocks and on the ground around it (ELGabry and others, Scientific Reports 16, 14032, 2026), found the pyramid’s fundamental frequency between 2.0 and 2.6 Hz, “with an average of ~ 2.3”, and “the average predominant frequency on the surrounding ground is about 0.60 Hz”. The survey reports spectral ratios, not absolute levels. We have found no open, absolute measurement of ambient motion on the plateau itself; the city’s traffic will raise it above Kottamya’s above about 1 Hz, by an amount still to be sourced.

The ground’s own waves are kilometres long where they are strong, and metres long only where they are local

Fifteen metres from a road, a passing truck shakes the ground a thousand times harder than the microseisms

Near the roads the ground shakes hardest, and still out of the satellite’s reach

Worst case by construction: every mapped road carries a truck at its point nearest each spot, with the manual’s levels 15 m away, falling off as a surface wave does (Caltrans 2020, Eq. 6) between undamped rock and the most damping rock-like ground in its tables. Roads from OpenStreetMap. The map marks where a truck would shake the ground faster than 77 µm/s, the first investigation’s velocity floor, which the satellite simulation showed is the scatter of a reading that registers little ground motion (R4, corrected). A typical truck never does; a truck over a bump does within 25 m of the road.

Even with a truck on every road at its nearest point, ambient motion reaches the radar's 77 um/s floor only within 25 m of a road, and only for a truck over a bump (17% of the plateau); a typical truck never does. Khafre's centre is 199 m from the nearest mapped road; the microseisms are 1,571 times below the floor everywhere.

What one satellite pass could detect is 1,300 to 18,400 times Giza’s microseisms

The microseisms near Giza move the ground 0.049 µm/s; even Peterson’s high-noise model, the world’s noisiest stations, reaches 3.5 µm/s. Allowing every advantage, the smallest motion one ICEYE dwell could detect is about 62 µm/s on a bright stone and 900 µm/s on plain ground (P2-05), and a chamber changes the ground’s motion by only a ten-thousandth of it (P2-04). The first investigation’s 77 µm/s “floor” (R4) was the scatter of a reading that recovers 1% of real ground motion, and its 0.1–10 µm/s for ambient motion had no source; both are replaced here by measurement.

If the seismic lab continues: the ambient field in every site