The rate of fault motion is calculated by combining the new surface ages, determined from crater density analysis and the measurement of maximum observed throw. This is then converted into a total cumulative moment release on each fault, integrated over their assumed ages. In order to do this, we assume a uniform temporal distribution of activity since the fault genesis. We consider this a reasonable assumption, since it is likely that a feature of this size was formed gradually, over geological timescales. There is also evidence of a long history of activity, certainly through the Amazonian, as shown by Vetterlein and Roberts . The total moment release, M0 over the age of the faults is given by the following:
where μ is the shear modulus, A is the fault surface area and is the total length-averaged slip. For Mars, μis generally thought to lie between 20 and 40 GPa [Knapmeyer et al., 2006; Grott et al., 2005; Schultz, 2003; Turcotte et al., 2002], taken here to be 30 ± 10 GPa. A is calculated from fault length, L and assumed fault depth, D. The relationship governing the ratio of fault depth to length in analogous terrestrial intraplate settings of normal and strike slip faults is given by Leonard :
However, given the large (>1000 km) lateral extent of the fault system, this calculation results in unphysical estimates of faulting depth. In all cases, the calculated depth exceeds the depth estimated for the elastic thickness of the lithosphere of the Elysium Planitia, of around 50 km (20–50 km [Comer et al., 1985], 50 ± 12 km [Wieczorek and Zuber, 2004], and 56 ± 20 km [Belleguic et al., 2005]). We, therefore, limit the depth of each fault to the depth of the elastic thickness in the region—50 km; a reasonable estimate for a major graben system of this kind. There is evidence that the faults may be segmented, which would affect the depth of faulting. Treating the segments as individual faults would significantly decrease the faulted depth. However, recent work by Hauber et al.  shows that as fault segments like this grow, they approach the character of a single fault. Work by Vetterlein and Roberts [2010, Figure 3] also shows that the Cerberus Fossae segments appear to behave as a single fault system in terms of the displacement length profile. We, therefore, assume the segments to be fully linked and treat them as such when determining depth of faulting.
 Though it is impossible to quantify the extent to which aeolian, and perhaps fluvial, processes have eroded the faults, the generic terrestrial longitudinal fault profile [Scholz et al., 1993] can be used to predict that the length-averaged slip, is approximately half of the maximum observed throw, SMAX. Taking = SMAX/2 will lead to a conservative estimate of slip rate that assumes no erosion, consistent with the aim of providing a lower-bound estimate of moment release rate. It should be noted that this length-averaged slip was doubled in the calculation to account for the dual nature of a graben system, which has two parallel antidipping faults.
 Using these figures of measured fault lengths and length-averaged slip, the total cumulative moment release on each of the graben systems is calculated to be 0.5–9.5×1023Nm (see Table 2). The summed moment release rates represent a total annual seismic moment release of , assuming all energy is released seismically and that there is no strike-slip component of motion (Figure 6).
Figure 6. Composite THEMIS image of the Cerberus Fossae, (15 °N, 170 °E [NASA/JPL-Caltech/ASU]), showing two features of interest. (a) Fault segmentation and en echelon features could result in overestimate of moment release. However, faults are likely to conjoin at depth, minimizing the effect of this error. (b) Preexisting mesa, bisected by one of the graben systems. It is clear that there has been little to no horizontal component of strike-slip motion on these faults.
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 This figure is striking since it is comparable to global annual moment budgets calculated in other works (1018 Nm/yr [Golombek et al., 1992], 3.42×1016to 4.78×1018 Nm/yr [Knapmeyer et al., 2006]), implying that Mars could be more seismically active than previous estimates suggest or that the fault depth has been overestimated (see section 5.2).
 One potential source of error is the possibility that the faults may no longer be active or that motion is taken up aseismically. There seems, however, to be compelling evidence that Cerberus Fossae are still active (with boulder trails and geologically recent volcanic and aqueous activity) and that the energy is released in discrete seismic events. The Martian crust itself is cold and rigid, capable of supporting the huge edifice of Olympus Mons for several billion years [Arkani-Hamed and Riendler, 2002]. This makes aseismic motion close to the surface or on faults with a surface expression, unlikely.