The Main Recent Fault is a major right‐lateral strike‐slip fault in the western Zagros mountains of Iran. Recent geodetic and geological studies estimate a low slip rate of 1–6 mm/yr at an unknown depth which, when combined with a non‐ideal fault geometry, makes the Main Recent Fault a difficult but interesting target for InSAR analysis. This analysis would further cement the estimated slip rate and provide an opportunity of estimate the depth to the base of the locked seismogenic zone, both important constraints on the seismic hazard posed by the fault, as well as for understanding how oblique convergence is accommodated and partitioned across the Zagros. We use 200 Sentinel‐1 SAR images from the past 5 years, spanning two ascending and two descending tracks, to estimate the first InSAR‐derived slip rate and locking depth for a 300 km long section of the fault. We utilize two established processing systems, LiCSAR and LiCSBAS, to produce interferograms and perform time series analysis, respectively. We constrain north‐south motion using GNSS observations, decompose our InSAR line‐of‐sight velocities into fault‐parallel and vertical motion, and fit 1‐D screw dislocation models to three fault‐perpendicular profiles of fault‐parallel velocity, following a Bayesian approach to estimate the posterior probability distribution on the fault parameters. We estimate an interseismic slip velocity of 2.4 ± 1.2 mm/yr below a loosely constrained 14 km locking depth, the first such estimate for the fault, and discuss the challenges in constraining the locking depth for low magnitude interseismic signals.

Lanzarote is the northern and eastern-most Canary Island, located in the eastern Atlantic Ocean near the continental margin and about 100 km off the west coast of Africa (Figure 1a). Like the surrounding archipelago, it is a small volcanic intraplate oceanic island, mostly probably created over the last 15 million years from hot spot volcanism in the Miocene, Pliocene and the Quaternary (Carracedo et al., 1998;Hoernle & Schmincke, 1993). The long-term evolution of the islands, and the degree to which tectonic processes influence this, is still a matter of ongoing debate (Anguita & Hernán, 2000;Blanco-Montenegro et al., 2018;Negredo et al., 2022). The Lanzarote style of eruption activity is typified by low-explosive outpourings of basaltic magma from fissures (Carracedo et al., 1992). The largest of these events in the past half millennium was the 6-year intermittent eruption between 1730 and 1736, where an estimated 3-5 km 3 (Carracedo, 2014) of material was erupted over much of the island of Lanzarote (Figure 1a). This eruption is also the third largest historical basaltic fissure eruption in the last 1,100 years behind a pair of Icelandic eruptions in 1783-84 Laki (Lakagígar), comprising 14 km 3 of lava

The Main Recent Fault (MRF) is a 800 km long dextral stike-slip fault in the hinterlands of the Zagros mountains, Iran. The fault is one of the most seismically active in the northwestern Zagros, having experienced historical earthquakes up to M s 7.4 (Ambraseys & Moinfar, 1973;Ghods et al., 2012;Karasözen et al., 2019), driven by convergence between the Arabian and Eurasian plates. During the interseismic period of the earthquake cycle, the MRF can be viewed as accumulating strain in the locked upper crust whilst slipping aseismically at depth, following that assumed for other strike-slip fault zones (Savage, 2000;Savage & Prescott, 1978;Thatcher, 1983;Wright et al., 2013). Estimates of interseismic slip rate and the depth-extent of the locked seismogenic zone, from here on referred to as the "locking depth", are critical to our understanding of both the local seismic hazard (Smith-Konter & Sandwell, 2009), and the accommodation of oblique convergence across the Zagros. Previous studies of the MRF have used a range of geological markers, geomorphological offsets, cosmogenic isotope dating, and Global Navigation Satellite System (GNSS) measurements to estimate a wide range (1-17 mm/yr) of possible slip rates (Table 1). The average slip rates determined from long-term geological/geomorphological offsets (1