Estimation of fault models for short-term slow slip events from groundwater pressure in soft sedimentary layers

Earth, Planets and Space

Table 1 Tidal components and the associated crustal strain sensitivities of groundwater level fluctuations at HKSi

	Tidal component of groundwater level				Tidal component of theoretical volumetric strain by modified GOTIC2				Crustal strain sensitivity of groundwater level
	M2 (period 12.4 h)		O1 (period 25.8 h)		M2		O1		for M2		for O1
	Amplitude (mm)	Phase (°)	Amplitude (mm)	Phase (°)	Amplitude (1e−8)	Phase (°)	Amplitude (1e−8)	Phase (°)	Amplitude (mm/1e−8)	Phase (°)	Amplitude (mm/1e−8)	Phase (°)
Before sealing	0.445 (0.009)	− 70.052 (1.159)	0.472 (0.049)	− 61.157 (5.904)	0.88352	− 3.338	0.57689	0.457	0.504 (0.010)	− 66.714 (1.159)	0.818 (0.085)	− 61.614 (5.904)
After sealing	4.399 (0.033)	− 7.276 (0.433)	3.274 (0.128)	− 2.287 (2.235)	0.88352	− 3.338	0.57689	0.457	4.979 (0.037)	− 3.938 (0.433)	5.675 (0.222)	− 2.744 (2.235)

Values in parentheses show root mean square errors estimated by BAYTAP-G (Tamura et al. 1991). The phase of the tidal component of the groundwater level is defined as 0° with reference to the decrease of the groundwater level during the dilatation in volumetric strain of solid earth tide. The phase of the tidal component of the theoretical volumetric strain is defined as 0° with reference to the dilatation of the theoretical volumetric strain during the dilatation in volumetric strain of solid earth tide. The phase shift of the crustal strain sensitivity is defined as 0° when the groundwater level decreases during dilatation in theoretical volumetric strain. Negative phase shifts indicate lag