Figure 2: (a) A site photo showing the deep borehole extensometer and the collocated GPS station (TXEX) at the Clear Lake site. The GPS antenna is mounted on the extended inner pipe of the extensometer borehole, which is anchored in the strata 936 m below the ground surface. (b) A sketch depicting the local aquifers and borehole extensometers (−936 and −530 m) at Clear Lake and a nearby shallow extensometer (−235 m) at Johnson Space Center (JSC). The horizontal distance between the two extensometers at the Clear Lake site is 100 m. The horizontal distance between the Clear Lake and JSC sites is 2.5 km.