After the earthquake of May 26th, the overall ITF status worsened. Today's commissioning work have tuned TCS and alignment working point, but despite the Dark Fringe and sideband levels came back to their original values, the problem stayed.

Looking at the sensitivity curve, more structures are present between 100 and 500 Hz, besides the overall flat noise level which seems to be increrased (figure 1). Looking at the Bruco, there seem to be a coherence with the accelerometers close to the squeezing pipe (figure 2) and to the detection bench for the structures between 300-400 Hz (figure 3). Finally, the structures around 160 Hz seems to be coherent with the BPC signals (figure 4). However, this latter structures are decreasing progressively after the TCS/ISC shift, hinting to an improvement of the CMRF and therefore a lower coupling of the common noises. 

From the time signals, a jump is visible particularly on the B1p camera Y position (SDB2_B1p_Cam_FitPosY) between before/after the earthquake (figure 5). A similar effect seem to be present also on B5 beam Y position, although very small.This could probably hint to a different position of the beam on the detection bench, possibly clipping and giving rise to stray light.

What looks also strange is B1s2, which decreases after the earthquake, despite of B1p and B1s1 whose bottom level stays almost the same. Does it hint to more light coupled through the second OMC? 

It would be good if the problem could be further investigated by DET experts.