Frictional and structural controls of seismic super-cycles at the Japan trench

Earth, Planets and Space

Table 1 Summary of the physical parameters controlling fault dynamics

Parameter	Symbol	Megasplay	Frontal prism	Forearc upper crust	Forearc basement
Static friction coefficient	\(\mu _0\)	0.6	0.3	0.3	0.6
Effective normal stress	\({\bar{\sigma }}\)	20 MPa	60 MPa	110 MPa	110 MPa
Direct-effect parameter	a	\(1\times 10^{-2}\)	\(1\times 10^{-2}\)	\(1\times 10^{-2}\)	\(1\times 10^{-2}\)
Steady-state parameter	\(b-a\)	\(4.0\times 10^{-3}\)	\(8.0\times 10^{-3}\)	\(4.0\times 10^{-3}\)	\(4.0\times 10^{-3}\)
Characteristic weakening distance	L	8 cm	8 cm	5 mm	1 cm
Loading rate	\(V_\text {L}\)	31 mm/year	52 mm/year	84 mm/year	84 mm/year
Segment width	W	21.2 km	60 km	24 km	58 km
Fault dip	\(\phi\)	15.74\(^\circ\)	5.5\(^\circ\)	5.0\(^\circ\)	10.6\(^\circ\)

Parameter	Symbol	Arc lower crust	Mantle wedge corner	Cold nose	Upper mantle
Static friction coefficient	\(\mu _0\)	0.6	0.3	0.6	0.6
Effective normal stress	\({\bar{\sigma }}\)	70 MPa	20 MPa	80 MPa	80 MPa
Direct-effect parameter	a	\(2\times 10^{-2}\)	\(2\times 10^{-2}\)	\(1\times 10^{-2}\)	\(2\times 10^{-2}\)
Steady-state parameter	\(b-a\)	\(-\,8.0\times 10^{-3}\)	\(2.0\times 10^{-3}\)	\(-\,2.0\times 10^{-3}\)	\(-\,1.0\times 10^{-3}\)
Characteristic weakening distance	L	10 cm	5 mm	2.5 cm	20 cm
Loading rate	\(V_\text {L}\)	84 mm/year	84 mm/year	84 mm/year	84 mm/year
Segment width	W	11 km	44.8 km	53.5 km	32 km
Fault dip	\(\phi\)	10.6\(^\circ\)	30.0\(^\circ\)	30.0\(^\circ\)	31.0\(^\circ\)

The model assumes uniform elastic properties with a shear modulus of \(G=30\) GPa, Poisson’s ratio \(\nu =0.25\), and shear wave speed \(V_S=3\times 10^{3}\) m/s. The reference slip velocity is \(V_0=10^{-6}\) m/s