Seismic versus aseismic slip for the 2023 Kahramanmaraş earthquake doublet

Domain: earth_science
Published: 2025-01-22
Editorial outcome: major_revision

Abstract
Interplay between seismic and aseismic slip could shed light on the frictional properties and seismic potential of faults. The well-recorded 2023 Kahramanmaraş earthquake doublet provides an excellent opportunity to understand their partitioning on strike-slip faults. Here, we utilize InSAR and strong motion data to derive the coseismic rupture during the doublet, ~4-month postseismic afterslip, and slip distributions of two Mw > 6.0 aftershocks. Our results show that afterslip appears to be complementary to coseismic slip and aftershocks, accounting for ~11.3% of the coseismic moment. Aftershocks mainly fall within the regions of positive Coulomb stresses caused by afterslip and follow a temporal decay similar to that of afterslip, indicating that aftershock production is the failure of small asperities loaded by the afterslip. The early postseismic afterslip is released ~93.7% aseismically and ~6.3% seismically by aftershocks. Our modeling results thus depict a complex fault system with highly variable slip patterns and stresses.

Introduction
Elastic rebound theory states that elastic stress/strain across an active fault accumulated during the interseismic period is released by sudden slip during an earthquake1. Thereafter, strain release continues, which is controlled by postseismic aseismic afterslip2–5. Seismic and aseismic slip are two main modes of fault behavior, with their spatial distribution shedding some light on the frictional properties of faults and serving as an indicator of the seismic potential6–8. Therefore, understanding the partitioning of seismic and aseismic fault slip is the core of seismotectonics6,9.

The East Anatolian Fault Zone (EAFZ) is a ~600-km sinistral strike-slip fault that connects the Dead Sea Fault Zone (DSFZ) to the Karlıova Triple Junction10,11. It accommodates the relative motion between the Arabian and Anatolian plates at a slip rate of ~10 mm/yr on the northeast side to ~4 mm/yr on the southwest side12–16. The EAFZ is divided into several major segments, and each of them is defined by bends, compressional structures, or pull-apart basins, as well as multiple subparallel and seismically active branches10,17,18.

The fault section of the EAFZ stretching from the Erkenek segment (ES) to the Amanos segment (AS) is characterized by a seismic recurrence interval of hundreds to millennia10, high interseismic coupling16,19, moderate strain rate20, and low seismicity rate21–23, indicating that it is capable of producing large earthquakes24. At 01:17 on 6 February 2023 (UTC time), the Mw 7.8 Nurdağı-Pazarcık earthquake struck this section, followed ~11 minutes later by an Mw 6.6 aftershock (hereafter called the 06/02/2023 aftershock). After over 9 h, the Mw 7.7 Ekinözü earthquake occurred ~97 km NNE of the 1st earthquake, which, along with the Mw 7.8 mainshock, is referred to as the Kahramanmaraş earthquake doublet. On 20 February 2023, the Mw 6.3 Antakya aftershock struck the southwestern termination of the Mw 7.8 Nurdağı-Pazarcık earthquake25 (Fig. 1). The series of strong shocks resulted in over 59,000 deaths and 110,000 injuries26,27.

The 2023 Kahramanmaraş earthquake doublet drew the attention of the community and seismologists around the world. After these two events, back-projection imaging, aftershock relocation, rupture dynamics simulation, multi-point source, and finite fault inversion were rapidly performed to decipher their fault geometries, source parameters, and rupture properties19,25,28–38. A consensus is that the 1st mainshock originated from an unmapped fault branch linked to the Pazarcık segment (PS) and then propagated bilaterally along the EAFZ for about 300 km, which imposed significant positive static stresses on the hypocentral region of the 2nd mainshock33. However, information on the postseismic deformation and mechanism following the Kahramanmaraş doublet is still unclear, limiting our knowledge of the fault slip budget of the EAFZ and the assessment of future seismic hazards. Therefore, a joint analysis of seismic and aseismic fault slips during and after this doublet is necessary. It is also important to understand the mechanical basis of stress buildup and release in continental strike-slip fault zones.

In this study, we utilize the strong-motion observations and Interferometric Synthetic Aperture Radar (InSAR) data from Sentinel-1 and ALOS-2 satellites to invert for the coseismic fault slip associated with the 2023 Kahramanmaraş doublet and two strong aftershocks with Mw > 6.0. Additionally, we investigate the postseismic afterslip within the first ~4 months and the interplay between aseismic and seismic fault slip. Finally, we discuss the seismic potential of the surrounding major faults.

Results
Coseismic rupture during the Kahramanmaraş doublet
The coseismic deformation derived from the Sentinel-1 and ALOS-2 SAR images is utilized to constrain the detailed coseismic slip distribution (see Methods, Supplementary Figs. 1 and 2a). Figure 2a and Supplementary Fig. 3 are veal that the majority of coseismic slip is confined to depths above 15–20 km, consistent with the average seismogenic thickness18. The 2023 Kahramanmaraş earthquake doublet is dominated by sinistral slip, accompanied by minor normal or reverse components, which is consistent with previous studies31,33. The main asperity of the Nurdağı-Pazarcık earthquake is located on the PS with a maximum slip of ~9 m. A more compact asperity with a peak slip of ~10 m is observed on the Çardak fault (ÇF) for the Ekinözü earthquake. Assuming a shear modulus of 30 GPa, the geodetic moments released by the Nurdağı-Pazarcık and Ekinözü earthquakes are ~6.5 × 1020 N·m and ~4.1 × 1020 N·m, respectively, corresponding to moment magnitudes of 7.8 and 7.7. The geodetic moment of the Nurdağı-Pazarcık event is slightly larger than the estimates from the United States Geological Survey (USGS) (5.4 × 1020 N·m) and the Global Centroid Moment Tensor (GCMT) (5.8 × 1020 N·m). And the geodetic moment released by the Ekinözü earthquake is between the seismic moments estimated by the USGS (2.6 × 1020 N·m) and GCMT (4.5 × 1020 N·m). Our preferred coseismic slip distribution is in good agreement with some published coseismic rupture models19,31,32,38–41, mainly because we all use InSAR data. These models consistently demonstrate that the high slip is concentrated in the shallow crust above depths of 15–20 km, with similar slip magnitudes and patterns. Some detailed discrepancies are attributed to different fault geometries, datasets, and inversion methods. For example, previous models did not consider the contribution of the Sürgü fault (SF) due to the lack of significant displacement discontinuities31,37 and few aftershocks near the SF28,29. To align with the local fault structure10,42, the SF is added to our coseismic model. Results show that SF is characterized by a small slip, possibly due to the 1986 M ~6 earthquake sequence that occurred along this fault22,23,43. The kinematic models without the constraint of InSAR observations show a relatively discrete high-slip region33,34, emphasizing the need for near-field geodetic data.

As shown in Supplementary Fig. 4, the optimal slip model recovers the surface displacements from both the Sentinel-1 and ALOS-2 images satisfactorily. In addition, we conduct a jackknife sensitivity analysis to evaluate the reliability of slip estimation (see Methods). The maximum standard deviation of the slip is ~0.8 m (Supplementary Fig. 5a), which represents only ~8% of the coseismic slip. All of them highlight the reliability of the coseismic slip model of the earthquake doublet constrained by InSAR observations.

Slip distribution of two strong aftershocks
Since the 06/02/2023 aftershock occurred temporally between the Mw 7.8 Nurdağı-Pazarcık and the Mw 7.7 Ekinözü events, it is difficult to directly retrieve its coseismic deformation using InSAR technology. We thus use the strong-motion data (Fig. 1a) to resolve the kinematic slip evolution during the aftershock by the iterative deconvolution and stacking (IDS) method (see Methods). Supplementary Fig. 6 shows that in the first 4 s, the 06/02/2023 aftershock ruptures bilaterally along dip with its major propagation toward the updip direction, featuring a peak slip rate of ~0.4 m/s. Subsequently, it mainly propagates toward the updip and SE directions. However, the moment release becomes weak and dispersed in this stage, probably due to the discontinuous fault structures in this region. The average rupture velocity is slow at ~2.5 km/s. Most of the slip is concentrated within the depth range of 8-24 km, and the total seismic moment is ~9.0 × 1018 N·m (Mw 6.6). The maximum slip is ~1.2 m, which is located ~5.6 km SW of its epicenter (Fig. 2e and Supplementary Fig. 6). The good agreement between the observed and synthetic waveforms validates the robustness of our kinematic model associated with the 06/02/2023 aftershock (Supplementary Fig. 7).

For the Mw 6.3 Antakya aftershock, we estimate its slip distribution with InSAR observations (see Methods, Supplementary Fig. 2c, d). Figure 2f demonstrates the slip distribution of the Antakya aftershock, which is characterized by a dominant sinistral movement with a minor normal component. The high slip is mainly concentrated at depths ranging from 3 km to 15 km, which releases a geodetic moment of ~3.0 × 1018 N·m (Mw 6.3). Notably, InSAR observations may include some contributions from postseismic deformation following the Mw 7.8 Nurdağı-Pazarcık earthquake. Given the small coseismic slip and afterslip (as modeled below) associated with the Nurdağı-Pazarcık event in the Antakya region (Fig. 2), it is reasonable to ignore its postseismic effects. The slip model for the Mw 6.3 Antakya aftershock effectively reproduces the observed InSAR displacements (Supplementary Fig. 8), thereby confirming the validity of this assumption and the robustness of the model.

Kinematic afterslip model
We use the cumulative postseismic line-of-sight (LOS) displacements within the first ~4 months to derive the kinematic afterslip distribution of the 2023 Kahramanmaraş earthquake doublet, following the same strategy as the coseismic inversion (see Methods, Supplementary Figs. 2b, 9, and 10). The spatial distribution of afterslip is illustrated in Fig. 2b. The majority of afterslip occurs in regions with low coseismic slip, spatially complementing the coseismic asperities. Notably, the high-afterslip concentration zone is located on the ÇF, with a maximum slip of ~0.65 m at a depth of ~16 km. The total moment yielded by the kinematic afterslip model is ~1.2 × 1020 N·m, corresponding to a moment magnitude of 7.3.

As demonstrated in Supplementary Fig. 11, the surface LOS displacements predicted by the kinematic afterslip model are basically in agreement with the InSAR observations, suggesting that afterslip is the main driving mechanism for the near-field postseismic deformation ~4 months after the earthquake doublet. The jackknife resampling method is also utilized to assess the sensitivity of the inversion for afterslip (see Methods). The maximum standard deviation of the slip is ~0.03 m (Supplementary Fig. 5b), accounting for only ~5% of the afterslip. This suggests that the InSAR observations are able to constrain the kinematic afterslip distribution well.

Stress-driven afterslip model
To ensure the physical plausibility of the inferred afterslip and reduce the number of free parameters44, we consider a stress-driven forward model for the afterslip of the 2023 Kahramanmaraş earthquake doublet (see Methods). Figure 2c and Supplementary Fig. 3c illustrate the predicted afterslip distribution during the first ~4 months under the frame of the rate-strengthening friction, which releases a geodetic moment of ~1.1 × 1020 N·m (Mw 7.3). The stress-driven afterslip distribution resembles the pattern of kinematic afterslip, with the majority of the afterslip occurring downdip of the coseismic high-slip zones. However, the stress-driven afterslip is found to be more concentrated close to the coseismic asperities, where shear stress increases substantially caused by the mainshocks. The kinematic afterslip model is smoother and fails to capture significant slip gradients. Discrepancies between the kinematic and stress-driven afterslip models may be attributed to heterogeneous frictional parameters on the fault plane32,41,45, smoothness constraints46, inaccuracies in the driving source of the coseismic slip model, and contributions of other postseismic mechanisms47. The surface deformation predicted by the stress-driven afterslip closely matches the cumulative postseismic displacements derived from InSAR data, except for some near-field and far-field noise that the kinematic afterslip model also cannot recover well (Supplementary Fig. 12). Herein, although we do not directly use the InSAR time series to constrain the stress-driven afterslip, the predicted time series for Regions A and B are still in good agreement with the observations (Fig. 3a, c, d). Moreover, the slip uncertainties, as determined through statistical analysis (see Methods), are below 0.22 m (Supplementary Fig. 13a), further validating the robustness of the stress-driven afterslip model.

Optimal afterslip model
The stress-driven afterslip simulation excludes shallow afterslip because it requires exceedingly dense grids to accurately resolve near-surface fault patches46. To better model the observed postseismic deformation and quantify the shallow afterslip, we construct a combined model that incorporates both kinematic shallow afterslip and stress-driven deep afterslip (see Methods). Figure 2d and Supplementary Fig. 3d exhibit a superposition of the inferred shallow and deep afterslip due to the Kahramanmaraş earthquake doublet, highlighting the predominance of downdip afterslip, with shallow afterslip primarily concentrated on the ES. The total moment yielded by the combined afterslip model is ~1.2 × 1020 N·m (Mw 7.3), with ~88% attributable to the deep afterslip and ~12% to the shallow afterslip. The afterslip moment represents roughly 11.3% of the coseismic geodetic moment. As illustrated in Supplementary Fig. 14, the InSAR-observed cumulative postseismic transients are explained well by the combined afterslip model, displaying an improved fit compared to the stress-driven afterslip model (Supplementary Table 1), particularly for the near-field deformation. Furthermore, it improves the fit between the observed and modeled InSAR time series (Fig. 3c, d). We thus take the combined afterslip model as the optimal afterslip model for the Kahramanmaraş earthquake doublet. The small slip uncertainties for both shallow and deep afterslip further demonstrate the stability of our combined afterslip model (Supplementary Fig. 13b).

Coseismic and afterslip moment scaling
Figure 4 displays the estimated moments of afterslip and coseismic slip for the Kahramanmaraş earthquake doublet alongside 62 afterslip models from 47 other earthquakes48 (Supplementary Fig. 15 and Table 2). The results reveal that the afterslip moment (Maft 0) near-linearly increases with the coseismic moment (M0) of earthquakes, with a gradient of ~1.0 (Fig. 4a). The correlation between Maft 0 and M0 of the Kahramanmaraş earthquake doublet also agrees well with this trend. This is because Maft 0 is the result of the combined effects of the coseismic area and average slip48. Given that the large uncertainty in the Maft 0 estimates due to data and modeling factors can mask the dependence we would expect to see from the observational time window48 (Fig. 4a), we do not attempt to normalize the Maft 0 estimates for the observation period but rather consider the individual Maft 0 estimates here.

Further examination of the relationship between the relative afterslip moment (Mre = Maft 0 / M0) and corresponding M0 reveals that Mre varies by several orders of magnitude, with 94% of models suggesting a range between 1% and 100% (Fig. 4b). The majority of moment models cluster around 10%, indicating that Maft 0 may be an order of magnitude smaller than M0. Interestingly, Mre exhibits a weak negative correlation with M0, indicating that larger events are prone to less Mre. As shown in Fig. 4b, the relative afterslip moments of the Mw 7.8 Nurdağı-Pazarcık earthquake and the Mw 7.7 Ekinözü earthquake are ~0.11 and ~0.12, respectively, consistent with the correlation. Notably, this identified correlation may be due to publication bias48. A wider range of Maft 0 variability in smaller earthquakes (Fig. 4), compounded by a bias towards studying smaller earthquakes with greater Mre, may contribute to the observed pattern48.

Interplay between the coseismic slip, afterslip, and aftershocks
The coseismic and postseismic slip patterns provide valuable insights into how seismic and aseismic fault slip is partitioned6,49. As demonstrated in Fig. 2b–d, the kinematic, stress-driven, and optimal afterslip models all reveal that the short-term afterslip is mainly located downdip of the coseismic rupture. There seems to be little overlap between the coseismic and postseismic zones (Supplementary Fig. 3). Notably, the spatially complementary pattern between the coseismic slip and afterslip is common, which has been widely observed in other events elsewhere5,50,51. To further decipher their interplay, we calculate the Coulomb failure stress changes (ΔCFS) on the fault planes induced by the coseismic rupture (see Methods). As shown in Fig. 5a, the afterslip is concentrated in regions with positive ΔCFS due to the mainshocks, indicating that afterslip is indeed triggered by the coseismic slip.

In addition, we estimate the ΔCFS triggered by the optimal afterslip distribution. We find that most near-fault aftershocks29 (within a distance of 5 km of the fault plane) fall within the regions of positive ΔCFS caused by afterslip (~53%) rather than by the mainshocks (~30%) (Fig. 5a, b). This finding is further confirmed by the aftershock catalog from ref. 28., which reveals a higher proportion of aftershocks associated with afterslip (~59%) than with the coseismic slip (~19%). Similar phenomena are also observed in some aftershocks at a distance from the fault planes, which is discussed in a later section. It is no longer surprising that afterslip plays a central role in triggering aftershocks52,53, which has been widely reported elsewhere after other documented earthquakes45,54, such as the 2021 Mw 7.4 Maduo earthquake51 and the 2017 Mw 8.2 Chiapas earthquake50. One extreme view of aftershock production is the rupture of small asperities loaded by afterslip, favored by the similar temporal decay between aftershocks and afterslip54. As shown in Fig. 6c, the temporal evolution of the optimal afterslip model correlates well with aftershocks. Moreover, the spatial relationship between aftershocks and afterslip is found to be complementary over time (Supplementary Fig. 16). We thus argue that afterslip may drive the occurrence of aftershocks. Note that we cannot rule out the possibility of dynamic triggering55. To further understand the seismic and aseismic slip behaviors during the early postseismic period, we estimate the cumulative seismic moment released by aftershocks within ~4 months to be 7.5 × 1018 N·m (Mw 6.5) (Fig. 6d). Here, the frequency-magnitude distribution for the aftershock catalog reveals a completeness magnitude of 1.6 (see Methods), above which all aftershocks are considered. By comparing the aftershock moment with the geodetically derived postseismic moment, we find that ~6.3% of the postseismic afterslip is released by aftershocks. This indicates that the increased stress due to the coseismic slip is mainly released in an aseismic manner.

We also demonstrate the spatial distribution of background seismicity, aftershocks, as well as the coseismic slip and afterslip along dip (Fig. 5e–g). We find that the relocated background earthquakes along the EAFZ are active within a depth range of 4–22 km22, consistent with the dominant depth range of aftershocks. Additionally, most aftershocks28 are concentrated between the coseismic asperity and postseismic afterslip. Spatially, there exists a complementary Mw 7.8 Simeon of Island, Alaska earthquake54 and the 2015 Mw 7.8 Gorkha (Nepal) earthquake60, respectively. The parameters of (a-b)σ and V0 together control the evolutionary characteristics of afterslip45,46,61. A larger (a-b)σ indicates a lower degree of nonlinearity in the afterslip decay61. Variations in frictional properties may be attributed to differences in fault zone materials and physical conditions59. When assuming the effective normal stress σ = 260 MPa at 20 km under hydrostatic pore pressure conditions62, the corresponding value of the frictional parameter (a-b) is 0.012, which is close to the range of 10−3-10−2 suggested by laboratory measurements63,64.

Future seismic potential
The Mw 7.8 Nurdağı-Pazarcık earthquake ruptured ~300 km along the western EAFZ. This event occurred just 3 years after the devastating 2020 Mw 6.8 Elazığ earthquake that ruptured the central segment of EAFZ22,49,65, leaving a ~40-km seismically quiescent region (SQR)25,29,65 (Fig. 1h). Notably, the aftershock distribution connects these two events below ~10 km, which is consistent with the depth of interseismic seismicity18,29. Therefore, the SQR is located between the surface and ~10 km depth. The optimal afterslip model suggests that the accumulated energy within the SQR is released aseismically through afterslip (Fig. 2d), resulting in a stress shadow (Fig. 5b). Furthermore, it has been found to creep during the interseismic period49. These indicate that the SQR may be characterized by the rate-strengthening property2,66, preventing the coseismic rupture of the 2023 Mw 7.8 Nurdağı-Pazarcık earthquake and the 2020 Mw 6.8 Elazığ earthquake. Consequently, the likelihood of a strong earthquake occurring in this region in the near future is low. It is necessary to mention that the 1893 M ~7.1 and 1905 Ms 6.8 Malatya earthquakes occurred near the SQR67. However, in the absence of more precise information on the faulting extent for the 1893 and 1905 events22, it is unclear whether these two earthquakes ever ruptured the SQR, preventing us from further characterizing its slip behaviors and frictional properties.

The extensive rupture of the 2023 earthquake doublet releases accumulated strain and adjusts the stress conditions of surrounding regions68. Therefore, we employ the static ΔCFS to further comprehend the stress effects caused by the coseismic slip and afterslip of this earthquake doublet (Fig. 7). To analyze the triggering relationship among aftershocks, coseismic slip, and afterslip, we calculate the ΔCFS map at a depth of 10 km, utilizing the receiver fault’s geometry parameters aligned with the focal mechanism of the Mw 7.8 Nurdağı-Pazarcık earthquake from the USGS. As shown in Fig. 7c, d, aftershocks (in the depth interval of 10 ± 3 km) are mainly concentrated in regions with positive ΔCFS induced by afterslip rather than by the mainshocks, consistent with the above analysis on the fault plane (Fig. 5a, b). Moreover, ΔCFS is positive at the north end (Pürtürge) and south end (Antakya) of the seismogenic fault of the Mw 7.8 Nurdağı-Pazarcık earthquake due to the coseismic and postseismic slip. As a result, there may be a risk of strong aftershocks in these areas.

To further investigate the seismic potential of the major faults, we specially select 11 nearby faults as receiver faults. Their fault traces and geometries are referenced from the active faults database in Türkiye42 (Supplementary Table 3). The results reveal that the stress increase due to the coseismic slip exceeds 0.03 bar on the DSFZ (Fig. 7a), bringing the fault closer to failure, while afterslip has little effect on the DSFZ (Fig. 7b). Given the significantly increased ΔCFS on the DSFZ due to the Kahramanmaraş doublet and the fact that the DSFZ is highly coupled16, it has the potential to generate strong earthquakes and derives more attention. In addition, ΔCFS due to the coseismic slip and afterslip is positive on the northern faults, including the Gerger fault, the Malatya fault, the Narince fault, and the Pürtürge segment, which may push the next earthquake on these faults. These findings underscore the need for heightened monitoring and preparedness in these regions.

Methods
InSAR data processing
We process the Sentinel-1 SAR data using GMTSAR software69,70. We invoke the differential InSAR (D-InSAR) method to map the coseismic LOS displacements of the earthquake doublet, as well as the Mw 6.3 Antakya aftershock. The chronological information of SAR images is presented in Supplementary Table 4. To account for the topographic phase, we apply the 3-arc-second Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM). The interferograms are multi-looked with a ratio of 8:2 in range and azimuth and filtered using a 200 m-wavelength Gaussian filter. The dense near-field fringes pose a challenge in accurately unwrapping the phase. To mitigate its potential impact, we exclude the region with coherence values below 0.2 to create a near-fault decorrelation mask70 and allow a phase discontinuity when unwrapping with SNAPHU71. We obtain the coseismic deformation associated with the earthquake doublet after geocoding (Supplementary Fig. 1a, b). Notably, the absence of near-fault deformation constraints may hinder the accurate determination of the coseismic slip distribution. Fortunately, the longer wavelength of the ALOS-2 data (~23.6 cm compared to ~5.5 cm for the Sentinel-1) results in better phase coherence and enables accurate phase unwrapping in the proximity of the fault trace. Therefore, we additionally use the ALOS-2 ascending (T184) and descending (T077) downsampled data from the work of ref. 32. to recover the coseismic deformation caused by the Kahramanmaraş earthquake doublet.

To measure the early postseismic deformation associated with the earthquake doublet, we utilize the SBAS-InSAR method72,73 to process the Sentinel-1 SAR data. The ascending track, collected from 9 February 2023 to 3 July 2023, and the descending track, spanning from 10 February 2023 to 22 June 2023 (Supplementary Table 4), are processed accordingly. The interferogram pairs are generated by applying specific thresholds for the temporal baseline (set at 80 days) and the spatial baseline (set at 200 meters) (Supplementary Fig. 9). These interferograms undergo a multi-looking process with a factor of 16:4 (range: azimuth) and are subsequently filtered with a Gaussian filter of 400 meters wavelength. To minimize the impact of poor coherence pixels and retain the stable high-quality regions, we perform a stacking process on the coherence grids of the interferograms and exclude regions with mean coherence less than 0.1. The presence of noise caused by atmospheric perturbations in interferograms limits accurate mapping of the postseismic deformation20. Here, we utilize the Generic Atmospheric Correction Online Service (GACOS) corrections74 and the Common-Scene-Stacking (CSS) method75 to mitigate atmospheric effects. Finally, the time series of postseismic deformation is obtained (Supplementary Fig. 10).

Static coseismic slip inversion
To enhance computational efficiency while preserving essential information, we employ the gradient-based quadtree method to downsample the coseismic deformation fields of the earthquake doublet76. Finally, we retain 5418 and 5129 data samples from the Sentinel-1 ascending and descending orbits, respectively. Equal weights are assigned to the displacements obtained from ALOS-2 data during the inversion.

The steepest descent method (SDM)77 is adopted to estimate the detailed coseismic slip of the earthquake doublet. To calculate the surface displacements caused by fault slip, we employ a rectangular dislocation model embedded in an elastic half-space78. We identify the fault traces by combining previous studies41, relocated aftershocks28,29, coseismic and postseismic deformation (Fig. 1), and geological survey10,42. Eight fault segments, namely the AS, PS, ES, Nurdağı fault, SF, Doğanşehir fault, ÇF, and Yeşilköy fault, are adopted to invert the observed InSAR displacements (Fig. 1 and Supplementary Fig. 1). The dip angles are established based on the work of ref. 32. (Supplementary Table 5), which is grounded in the analysis of aftershock profiles. The fault plane is extended from the surface to 30 km along dip, and then is discretized into 852 rectangular sub-faults with a grid of ~5 km by 5 km. The rake angle is allowed to vary between -40° and 40°. The optimal smoothing factor is determined to be 0.1 based on the L-curve criterion (Supplementary Fig. 2a).

Two strong aftershock slip models
For the Mw 6.6 06/02/2023 aftershock, we use the strong-motion data to resolve its kinematic slip evolution. We access the strong-motion waveform data from the Department of Earthquake, Disaster and Emergency Management Authority of Türkiye (AFAD), and 14 stations with good azimuthal coverage are selected. We integrate the raw strong-motion accelerations twice into displacements and band-pass filter them in [0.02 0.2] Hz to escape the interference by long-period noise and the inadequacies of the theoretical Green functions at higher frequencies79. We apply the automatic inversion scheme based on the iterative deconvolution and stacking (IDS) method80 to determine its refined slip evolution. The rupture initiation (37.29°N, 36.93°E, 14.8 km) is adapted from the high-resolution relocation28. A rectangular fault plane is constructed with the strike and dip of 218° and 85°, respectively, based on the relocated aftershock distribution28. We use the code QSSP81 to calculate the Green’s function based on the CRUST1.0 model82.

For the Mw 6.3 Antakya aftershock, we process the Sentinel-1 SAR images from both ascending (T014) and descending (T021) tracks. The observed LOS displacements are shown in Supplementary Fig. 1c, d. Due to the smaller deformation area of the Mw 6.3 Antakya aftershock, we uniformly downsample its coseismic LOS displacement fields. The SDM approach is invoked to estimate the coseismic slip of the Antakya aftershock. We constrain the curved fault trace with the deformation and active fault datasets42. We determine the dip angle by systematically marching through a series of dips to arrive at the minimum root mean square of residuals (RMSR) between InSAR observations and predictions.

RMSR = sqrt(sum((d_obs - d_pre)^2) / n) (1)

where d_obs and d_pre denote the observed and predicted LOS displacements, respectively, and n is the number of data points. As shown in Supplementary Fig. 2c, the fault plane is determined as dipping to the northwest at 42°, consistent with the focal mechanism from the GCMT (strike/dip: 226°/42°). During the inversion, we divide the fault plane into 80 sub-faults with allowable rake angles between −70° and 30°. The smoothing factor of 0.05 is set to balance the model roughness and data misfit based on the trade-off curve (Supplementary Fig. 2d).

Kinematic afterslip inversion
The postseismic deformation may arise from the contributions of poroelasticity, afterslip, and viscoelastic relaxation83, among which afterslip has been identified as the primary mechanism responsible for the early postseismic deformation spanning from several days to months51,59. We thus perform a pure afterslip model to investigate the postseismic deformation of the earthquake doublet.

In general, the afterslip is distributed updip and downdip of the coseismic rupture. We thus extend the fault plane to 50 km for the postseismic afterslip model to recover the larger range of postseismic deformation (Supplementary Fig. 11). Considering the limitations of the CSS method in mitigating atmospheric noise at the end images59, we exclude the last few scenes to determine the postseismic deformation. We downsample the cumulative postseismic deformation for the ascending (9 February 2023 to 9 June 2023) and descending (10 February 2023 to 10 June 2023) tracks after applying a mask to exclude the region affected by the Mw 6.3 Antakya aftershock. We then estimate the kinematic afterslip based on the cumulative postseismic LOS displacements within the first ~4 months following the strategy of the coseismic slip inversion. The smoothing factor is the same as that in the coseismic inversion (Supplementary Fig. 2b).

Stress-driven afterslip simulation
We simulate the stress-driven afterslip evolution using the Unicycle program57,84–86. The fault afterslip controlled by the rate-strengthening simplification could be expressed as45:

V = 2V0 sinh(Δτ / ((a-b)σ)) (2)

where Δτ is shear stress loading induced by the coseismic rupture; σ is the effective normal stress on the fault; The friction parameter V0 represents the reference slip rate that controls the timescale of relaxation; (a-b) is the frictional parameter of the rate-and-state friction law.

The coseismic slip model is used as the stress-driving source. We deduce model parameters by seeking the most suitable values that can effectively recover the postseismic deformation, which is determined by minimizing the RMSR between InSAR observations and predictions. Through the trial-and-error approach, the best-fitting stress-driven model is identified, achieving a minimum RMSR of ~14.3 mm. Meanwhile, the optimal values of the frictional parameter and the reference slip rate are determined to be 3 MPa and 1.3 m/yr, respectively (Fig. 3b).

Optimal afterslip model
Taking into account both the physical reasonableness and the fit to the observed postseismic deformation, we thus develop a combined afterslip model that incorporates the stress-driven deep afterslip and kinematic shallow afterslip46. We first calculate the surface contributions of the optimal stress-driven afterslip model (V0: 1.3 m/yr; (a-b)σ: 3 MPa) and remove them from the InSAR observations. We then use the residual LOS displacements to estimate the distribution of shallow afterslip following the strategies of the kinematic afterslip inversion. In order to mitigate potential trade-offs with long-wavelength residuals, we exclude the residual displacements beyond 20 km from the fault trace.

Jackknife sensitivity analysis
We test the reliability of the coseismic slip and kinematic afterslip models using the jackknife resampling method87. We randomly remove 20% of downsampled InSAR data, and then rerun the inversion using the remaining data. Subsequently, we reperform the processes by randomly selecting another 20% of the data. We repeat this process 50 times and then calculate the standard deviations of slip for each fault patch. Supplementary Fig. 5 shows the distribution of standard deviations for the coseismic slip and kinematic afterslip.

Statistical uncertainty analysis
Due to various trade-offs among the parameters of the stress-driven afterslip model, the best-fitting model is only marginally superior to other relatively distinct models. To account for the uncertainties associated with the stress-driven and optimal afterslip models, we select models that are acceptable at the 68% confidence level88, ensuring a RMSR below 15.7 mm. Based on these selected models, we systematically calculate the slip uncertainties for each fault patch. Notably, the uncertainties for both the stress-driven and optimal afterslip models are less than 0.22 m, demonstrating the robustness of our afterslip models (Supplementary Fig. 13).

Coulomb failure stress changes
The Coulomb failure stress changes (ΔCFS) can be calculated based on the following formula:

ΔCFS = Δτ + μ0Δσn (3)

where Δτ and Δσn represent the changes in shear stress and normal stress, respectively. The effective friction coefficient μ0 is set at 0.4. A positive value of ΔCFS indicates that the induced stress changes bring the fault closer to rupture, while a negative ΔCFS value suggests the opposite effect. Our optimal coseismic slip and afterslip models are used as driving sources to calculate the stress changes due to the mainshocks and afterslip, respectively.

Completeness magnitude of the aftershock catalog
The completeness magnitude represents the lowest magnitude at which all earthquakes in a region are detected and reliably recorded. To accurately estimate the completeness magnitude for the AFAD aftershock catalog, we apply the maximum curvature method using Zmap7 software89. This method analyzes the frequency-magnitude distribution of earthquakes, focusing on the point of maximum curvature on this distribution curve. This point is indicative of the magnitude threshold above which all earthquakes are reliably recorded, and below which some smaller earthquakes might be undetected or omitted due to limitations in the detection capability of the seismic network.

Data availability
The Sentinel-1 SAR data used in this study are downloaded from the Alaska Satellite Facility (ASF, https://search.asf.alaska.edu/). The strong-motion data are available at https://zenodo.org/records/10081034. Sub-sampled LOS displacements from the ALOS-2 used in this study are available at https://doi.org/10.5281/zenodo.8128343. Coseismic and postseismic deformation derived from Sentinel-1 images, slip models, and the aftershock catalog from the AFAD project are available at https://doi.org/10.5281/zenodo.14223396.

Code availability
The SDM code can be found at ftp://ftp.gfz-potsdam.de/pub/home/turk/wang/. The Unicycle open-source software for modeling the stress-driven afterslip is available at https://bitbucket.org/sbarbot/unicycle/src/master/. The Zmap7 software can be found at github: https://github.com/CelsoReyes/zmap7.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "From the technical point of view, the tools and the results are satisfactory but the description of the motivation as well as the depth of the interpretation are not in the level of a scientific publication that is supposed to move our knowledge forward. It is written with a logic of a research report going through all technical details, which must rather mostly be part of the supplementary material. The manuscript would have a potential to be published if the results can be better discussed to be merged with the present knowledge on the 2023 Kahramanmaraş doublets in particular and mechanics of earthquakes and faults in general. However, its current shape needs to be significantly improved. In addition to this general comment, here I list some points to be clarified:\nL143: What does “controlling role” refer to?\nL162: How “the asperities” are identified?\nL163: Why the authors used “doesn’t” in written English?\nFig4: Result are dependent on observation period of the after slip. What is done to decompose this artificial effect?\nFig4b: On average, it indicates a drop in relative after slip moments as a function of increasing mainshock moment. How would it be interpreted.\nL250: What is meant by “divided”? Do the authors mean “partitioned”?\nL252: Do the results able to resolve the overlap between co- and post-seismic zones? If so, it needs to be quantified?\nL260-261: Can it be quantified? For example, a plot of co-seismic stress change versus after slip.\nL289: How it is quantified that all aftershocks are located on the fault plane? Or any selection made?\nL293: Are the uncertainty of hypocenters able to be reliably compared with the slip at this resolution? What are the uncertainties of the hypocenters?\nL307-313: Statements need to be supported by results, e.g. a plot of observations versus depth as well as uncertainties versus depth.\nL324-325: “diminished” is a very strong statement. How? There are event some aftershocks in the scale of strong earthquakes (M6+).\nL320-340: There is not a clear statement on what is found and what is its benefit.", "reviewer_2": "I enjoyed reading this InSAR-based analysis of the 2023 SE Turkey earthquake sequence, which to my knowledge is the first such study to focus on observations and mechanisms of triggered post-seismic afterslip and aftershocks. The key results are (1) that afterslip concentrates around the edges of coseismic slip asperities, and (2) that afterslip and aftershocks are closely linked both spatially and temporally, implying that aftershocks result from failure of small asperities loaded by the afterslip. These results are not entirely surprising, but this sequence provides one of the best datasets constraining these relations anywhere in the world, so the results are certainly significant to the field. The paper is well written and illustrated, and mostly well referenced (with a few exceptions, detailed below), and so I would urge publication following some minor revisions.\nMy detailed suggestions for revisions are provided as comments or edits in the attached PDF. The most important of these are further emphasized below.\n1) There is little emphasis on what was known about the EAF before 2023. In particular, I’d draw your attention to the calibrated, relocated seismicity presented by Pousse-Beltran et al. (2020), GRL, https://doi.org/10.1029/2020GL088136. Their Figure S9 shows that background seismicity extends to 18-20 km depth all along the EAF, which is significantly deeper than the 2-12 km range you cite in Line 293 (you do not reference this sentence, so I’m not sure where you get this range from). Note that Pousse-Beltran’s calibrated, multi-event relocated depths are far more reliable than single-event locations derived from routine catalogs.\nYou might also be interested to note Pousse-Beltran’s (2020) relocation of a pair of M 6 earthquakes in 1986 to along the Surgu fault. This may explain why you see a lack of slip along this fault in your coseismic models (Line 225).\nSimilarly, the seismic gap between the 2023 and 2020 earthquakes, in which you observe much afterslip, is also the location of two large historical earthquakes, in 1893 and 1905. These are plotted in Figure 1 of Pousse-Beltran et al. (2020), and the original reference for these is Ambraseys (1989), GJI, https://doi.org/10.1111/j.1365-246X.1989.tb04453.x. This part of the fault may have had some afterslip following the 2020 earthquake (check Cakir et al. 2023, which you already cite). Both of these things should be noted.\n2) In your analysis of the relationship between afterslip and aftershocks, you seem to assume that the latter all occur on the mainshock slip planes (or their direct continuations down-dip or along strike). But is this really the case? My understanding is that many of the aftershocks occurred some distance (perhaps up to several kilometers) away from the main fault plane. If this is the case, then I think that this should be discussed somewhere in the Section titled “Interplay between afterslip and aftershocks”.\n3) Most of the figures look nice but I find the colouring on Figure 5 garish, making it hard to distinguish the purple aftershocks from the red-blue CFS colour maps. I suggest muting the CFS colours, and perhaps changing the aftershocks from purple to black to let them stand out more.\n4) I’d prefer you to name faults that are part of the main, through-going East Anatolian Fault as “segments” rather than their own faults. You will therefore need to alter many of the acronyms given at the end of the Figure 1 caption. Your inset to Figure 1 implies a major plate boundary between the Aegean Sea and the Anatolia plate, where there is none. The Aegean is simply the rifted part of the western Anatolian plate, where this comes under the influence of the Hellenic trench.\nBest wishes,\nEdwin Nissen", "reviewer_3": "This manuscript presents observations and modeling of co-seismic and early post-seismic deformation due to a pair of major strike-slip earthquakes that occurred in southern Turkey last year. The authors use InSAR data to constrain finite fault models (FFMs) of coseismic slip and afterslip that occurred over a time period of 4 months after the events. They find that the observed post-seismic deformation is consistent with afterslip occurring at the periphery of high co-seismic slip areas (\"seismic asperities\"). The authors quantify the relative magnitudes of the co-seismic slip and afterslip, as well as the relative contributions of afterslip and aftershocks to the observed post-seismic deformation. They find that the moment release due to afterslip is a small fraction of the moment release due to the mainshock(s), and the moment release due to aftershocks is a small fraction of that due to afterslip. The authors also find that the co- and post-seismic slip on faults ruptured during the 2023 sequence have a complementary spatial pattern, as observed for many previous earthquakes. Finally, the authors derive slip models for two strong aftershocks, and calculate static stress changes on faults adjacent to the earthquake ruptures. The manuscript is generally well written, and the results appear to be technically sound. There have been a number of studies of the 2023 Turkey doublet, which is understandable given the earthquake size and impact. This study focuses on the interplay between seismic and postseismic processes, and presents some new (postseismic) data and interpretation that may be of interest to a broader community. I am happy to recommend publication in Nature Communications pending a moderate revision (mostly of editorial nature to improve the manuscript readability). My comments below are ordered by the line numbers, not by significance.\n1. line 19. \"... of faults\" (plural)\n2. line 23. \"this doublet\" - it's not clear whether \"doublet\" refers to the two mainshocks, or two aftershocks mentioned in the previous sentence. Please clarify, \"the 2023 Mw 7.8-7.7 doublet...\"\n3. line 27. Replace \"It\" with \"Afterslip\".\n4. line 28. \"consistent with the near-linearly coseismic and afterslip moment scale\"- I'm not sure what the authors with to say here. Grammatically, it should be \"near-linear ... scale\" (or scaling). Semantically, I don't see how the fraction of 10% signifies a linear scaling between coseismic slip and afterslip. Please elaborate.\n5. line 30. \"follow a similar temporal decay as afterslip\" -> \"follow a temporal decay similar to that of afterslip\"\n6. lines 45, 322. The 40 kilometer \"gap\" between the two earthquake ruptures is a controversial item. Some previous studies suggested it, while others did not. The data used in the manuscript have very limited coverage of the eastern tip of the M7.8 rupture to resolve this issue. I suggest removing the mention of this \"gap\" throughout the manuscript, or use additional data to better resolve it.\n7. line 54. \"are\" -> \"were\" (work done in previous studies)\n8. line 58. \"on the smaller event\" -> \"on the hypocentral region of the 2nd mainshock\"\n9. line 65. \"to invert the coseismic fault slip\" -> \"to invert for the coseismic fault slip\" (one inverts the data for the model parameters).\n10. line 72. \"Seismicity and data used in this study\" -> \"Seismicity and InSAR data used in this study\".\n11. line 73. InSAR frames and labels can be hardly seen in panel 1a - please use more contrasting colors.\n12. line 90. \"Coseismic deformation of the 2023 Kahramanmaraş earthquake doublet is mapped well by...\" -> \"Coseismic deformation due to the 2023 Kahramanmaraş earthquake doublet is well mapped by...\"\n13. line 124. \"We collect a total of...\" -> \"We use a total of...\" (data were collected by a satellite, not by the authors).\n14. line 128. \"deformation mainly arises from\" -> \"deformation may arise from\"\n15. line 133. What do the authors mean by \"deformation stability\"? Perhaps \"quasi-steady deformation pattern\"?\n16. line 137. \"coseismic slip is sparse\" -> \"coseismic slip is low\"\n17. line 160. \"occurring in the downdip of...\" -> \"occurring downdip of...\"\n18. line 218. \"Compared\" -> \"Comparison\"\n19. line 219. \"overlaps\" -> \"shares many common features\"\n20. line 220. \"because all of us invoke the SAR images...\" -> \"because our study uses the same SAR data as the previous studies\". Delete the rest of the sentence (\"with high spatial resolution during the inversion\").\n21. lines 233-235. Panels an and b in Fig. 4 are redundant, as they present the same data. Consider removing one of them. If you keep panel 4a, it would be useful to label the dashed lines \"100%\", \"10%\", \"1%\".\n22. lines 253-254. Complementary patterns of coseismic slip and afterslip was noted in a number of earlier studies, e.g. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JB011122\n23. line 323-324. \"the accumulated energy within the seismic gap is released aseismically through afterslip\" - if that is the case, the respective fault segment is velocity-strengthening, and cannot be referred to as \"the seismic gap\".\n24. line 328. \"on the neighboring major fault\" -> \"on neighboring major faults\"\n(the authors compute stress changes on several faults, not some specified fault).\n25. line 337-338. \"Given the DSFZ is highly coupled, it has a great likelihood of strong earthquakes in the near future, deriving more attention\" - this is an overstatement. The static Coulomb stress increase does not imply that a future rupture is imminent. Please rephrase or remove.\n26. line 363. \"facilitates the reduction of the phase gradient\" -> \"results in a better phase coherence\"\n27. line 364. \"additionally add\" -> \"additionally use\"."}, "author_response": "Response: Thanks for your detailed review and valuable feedback.\n1．We have added a paragraph to the Section “Introduction” to illustrate the importance of exploring partitioning of seismic and aseismic fault slip (motivation) in the revision.\n2．We have improved the current shape. Some technical details have been moved to the supplementary “Methods”.\n3．We have added a lot of in-depth discussion and relevant references in the Sections “Comparison with published coseismic slip models”, “Coseismic and afterslip moment scaling”, “Frictional properties”, and “Future seismic potential” in the revision.\nL143: What does “controlling role” refer to?\nResponse: Thanks for your suggestion. The postseismic deformation may arise from the contributions of poroelasticity, afterslip, and viscoelastic relaxation, among which afterslip has been identified as the primary mechanism responsible for the early postseismic deformation spanning from several days to months. As demonstrated in Supplementary Fig. 8, the surface LOS displacements predicted by the kinematic afterslip model agree well with the InSAR observations, suggesting that afterslip is the main driving mechanism for the near-field postseismic displacements following the earthquake doublet.\nTo make the expression clearer, we have modified it in the revision as follows,\n“afterslip is the main driving mechanism for the near-field postseismic deformation ~4 months after the earthquake doublet”\nL162: How “the asperities” are identified?\nResponse: Areas hosting large seismic slip are called asperities (e.g.,Lay and Kanamori,1981;Lay et al.,1982). In the framework of rate-and-state friction (e.g.,Scholz,1998), asperities are characterized by velocity-weakening frictional behavior (i.e., the friction rate parametera-b<0), indicating that seismic rupture may nucleate and easily propagate.\nL163: Why the authors used “doesn’t” in written English?\nResponse: Thanks for your suggestion. To make the description more robust, we have modified it in the revision as follows,\n“The kinematic afterslip model is smoother and fails to capture significant slip gradients.”\nFig4: Result are dependent on observation period of the after slip. What is done to decompose this artificial effect?\nResponse: Thanks for your suggestion.\n1.Based on 148 afterslip studies, Churchill et al. (2022) have suggested that there is no strong relationship between the afterslip moment (Maft ) and the observation start time and duration.\n0\n2.Different afterslip moments following the same earthquake can vary considerably due to data and modeling factors, which cannot be explained by the observation start time and duration (such as the 2004 Mw 6.0 Parkfield earthquake and the 2004 Mw 9.1 Sumatra earthquake, see the following Table). So, the relative uncertainty in afterslip moment estimates can obscure the dependence we expect to see from either the observation start time or duration. We thus do not attempt to normalize afterslip moment estimates for the observational time window and instead consider individual afterslip moment estimates following the strategy of Churchill et al. (2022).\n3.To enhance the clarity, we refined the related description, as follows:\n“Fig. 4 displays the estimated moments of afterslip and coseismic slip for the Kahramanmaraş earthquake doublet alongside 62 afterslip models from 47 other earthquakes (Churchill et al., 2022)”\nIn addition, to express more clearly the dependence of results and the observation period, we have added a relevant discussion in the revision as follows,\n“Note that we do not attempt to normalize the Maft estimates for the observation period, but rather\n0\nconsider the individual Maft estimates here. Because the large uncertainty in the Maft estimates due\n0 0\nto data and modeling factors can mask the dependence we would expect to see from the observational time window (Churchill et al., 2022) (Fig. 4a).”\nEnd Time (days\nEvent M (Nm) Maft (Nm) Maft /M (%) \n0 since mainshock) 0 0 0\n30 2.44E+22 36.5\n152 3.70E+22 55.4\nParkfield (2004)\n1.14E+18 548 1.24E+22 18.6\nMw 6.0\n730 3.40E+18 299.3\n913 3.76E+18 331\n1826 1.57E+18 138.2\n30 2.44E+22 36.5\n152 3.70E+22 55.4\nSumatra (2004) 6.68E+22 548 1.24E+22 18.6\nMw 9.1 768 8.10E+21 12.1\n1004 2.24E+21 3.4\n1446 2.45E+21 3.7\nFig4b: On average, it indicates a drop in relative after slip moments as a function of increasing mainshock moment. How would it be interpreted.\nResponse: Thanks for your suggestion.\n1．As shown in Fig. 4b, the relative afterslip moment (Maft /M ) indeed weakly and negatively\n0 0\ncorrelates with the mainshock moment (M ). Notably, a greater scope for relative afterslip variability\n0\nin smaller earthquakes, combined with a publication bias whereby smaller earthquakes with larger relative afterslip moments are preferentially studied, provides one explanation for the relationship we observe but implies that it may be due to the publication bias.\n2．We have added a related discussion in the revision as follows,\n“Further examination of the relationship between the relative afterslip moment (M =Maft /M ) and\nre 0 0\ncorresponding M reveals that M varies by several orders of magnitude, with 94% of models\n0 re\nsuggesting a range between 1% and 100% (Fig. 4b). The majority of moment models cluster around 10%, indicating that Maft may be an order of magnitude smaller than M . Interestingly, M exhibits\n0 0 re\na weak negative correlation with M , indicating that larger events are prone to less M . As shown\n0 re\nin Fig. 4b, the relative afterslip moments of the Mw 7.8 Nurdağı-Pazarcık earthquake and the Mw 7.7 Ekinözü earthquake are ~0.10 and ~0.11, respectively, consistent with the correlation. Notably, this identified correlation may be due to the publication bias (Churchill et al., 2022). A wider range of Maft variability in smaller earthquakes (Fig. 4), compounded by a bias towards studying smaller\n0\nearthquakes with greater Maft , may contribute to the observed pattern (Churchill et al., 2022).”\nResponse: Thanks for your suggestion. Yes, “partitioned” is more appropriate. And we have modified it in the revision.\nL252: Do the results able to resolve the overlap between co- and post-seismic zones? If so, it needs to be quantified?\nResponse: Thanks for your suggestion.\n1. Our results are able to resolve the overlap between coseismic and postseismic zones. However, given the significant slip magnitude difference between coseismic slip and afterslip, their spatial distribution relationship is usually judged visually.\n2. To better demonstrate the spatial relationship between coseismic slip and afterslip, we have drawn the coseismic slip contours in the afterslip distribution (Supplementary Fig. 3). As shown in Supplementary Fig. 3, the kinematic, stress-driven, and optimal afterslip models all illustrate that the short-term afterslip predominantly occurs downdip of the coseismic rupture, with no significant overlap between the coseismic slip and afterslip for the 2023 Kahramanmaraş earthquake doublet.\nL260-261: Can it be quantified? For example, a plot of co-seismic stress change versus after slip.\nResponse: Thanks for your suggestion. We have plotted the afterslip contours in Fig. 5a, which demonstrates the relationship between the coseismic stress changes and afterslip.\nL289: How it is quantified that all aftershocks are located on the fault plane? Or any selection made?\nResponse: Thanks for your suggestion. There are indeed some aftershocks that occurred away from the main fault planes. To discuss the interplay between aftershocks and afterslip more robustly, we carried out different aftershock selections for different issues. The details are as follows:\n1.To investigate the spatial and triggering relationship between aftershocks and afterslip on the fault planes, we selected “near-fault” aftershocks within 5 km of the seismogenic faults following the strategy of Churchill et al. (2024) (Fig. 5b).\n2.To further discuss the triggering relationship between afterslip and aftershocks at a distance from the main fault planes, we have calculated the stress change map at the depth of 10 km. Here, we selected aftershocks in the depth interval of 10±3 km (Fig. 7d).\n3.To decipher the temporal decay pattern of aftershocks and that of afterslip, and compare the seismic moment released by aftershocks to the geodetically derived postseismic moment, we selected all aftershocks above the completeness magnitude following the strategy of Zhao et al. (2022) (Figs. 6c and 6d).\nIn addition, we have specified the principles of aftershock selection and added the related discussion in the revision.\nL293: Are the uncertainty of hypocenters able to be reliably compared with the slip at this resolution? What are the uncertainties of the hypocenters?\nResponse: Thanks for your suggestion. Here we adopted the background seismicity catalog from Pousse-Beltran et al. (2020), which involved over 300 relocated seismic events using the mloc program along the East Anatolian fault since 1971. The hypocenters are reliably compared with the slip at this resolution, with an uncertainty of <1 km (Pousse-Beltran et al., 2020).\nL307-313: Statements need to be supported by results, e.g. a plot of observations versus depth as well as uncertainties versus depth.\nResponse: Thanks for your suggestion.\n1．Different slip behaviors (seismic and aseismic slip) reflect the frictional properties of the fault plane (Avouac, 2015). Under the framework of rate-and-state friction, earthquakes can only occur in locked regions appearing to be rate-weakening, whereas the rate-strengthening zones are dominantly characterized by afterslip (Avouac, 2015). Therefore, the coseismic slip and afterslip should not overlap significantly, especially when using simple layered crust models (Hillers et al., 2006). As shown in Fig. 2 and Supplementary Fig. 3, the majority of coseismic slip is confined to a depth range of <15-20 km, while afterslip predominantly occurs downdip of the coseismic high-slip zones, consistent with the expected slip pattern. This distribution pattern thus indicates an estimated transition depth of 15-20 km from the rate-weakening zone to the rate-strengthening zone.\n2．To be clearer, we have added the related results and discussion in the revision, as follows:\n“Our obtained coseismic and postseismic slip models associated with the Kahramanmaraş earthquake doublet demonstrate that the frictional behaviors of the EAFZ vary with depth. Under the framework of rate-and-state friction, earthquakes can only occur in locked regions appearing to be rate-weakening, whereas the rate-strengthening zones are dominantly characterized by afterslip (Avouac, 2015). Therefore, the coseismic slip and afterslip should not overlap significantly, especially when using simple layered crust models (Hillers et al., 2006). As shown in Fig. 2 and Supplementary Fig. 3, the coseismic slip is concentrated within a depth range of less than 15-20 km, while the afterslip predominantly occurs downdip of the coseismic high-slip zones, in line with the expected slip pattern. We thus argue for a transition from a rate weakening in the shallow crust (<15-20 km) to a rate strengthening or steadily creeping region at greater depths.”\nL324-325: “diminished” is a very strong statement. How? There are event some aftershocks in the scale of strong earthquakes (M6+).\nResponse: Thanks for your suggestion.\n1．Our optimal afterslip model suggests that the shallow afterslip is observed within the seismically quiescent region (SQR), indicating that the SQR may be characterized by rate-strengthening properties (Guo et al., 2020; Yue et al., 2017).\n2．In addition, strong aftershocks (M6+) occurred near the Pazarcık segment (Mw 6.6) and Amanos segment (Mw 6.3), with few aftershocks occurring within the seismically quiescent region.\n3．To make the expression more robust, we have revised it in the revision as follows:\n“Our optimal afterslip model suggests that the accumulated energy within the SQR is released aseismically through afterslip (Fig. 2d), resulting in a stress shadow (Fig. 5b). It indicates that the SQR may be characterized by the rate-strengthening property (Guo et al., 2020; Yue et al., 2017), preventing the coseismic rupture of the 2023 Mw 7.8 Nurdağı-Pazarcık earthquake and the 2020 Mw 6.8 Elazığ earthquake. Consequently, the likelihood of a strong earthquake occurring in this region in the near future is low”\nL320-340: There is not a clear statement on what is found and what is its benefit.\nResponse: Thanks for your suggestion. In this section, we delve into the future seismic potential insights drawn from the 2023 Kahramanmaraş earthquake doublet. These findings highlight the critical need for increased monitoring and preparedness in these regions. The significance of this section is threefold:\n1. Our results indicate that the accumulated energy within the seismically quiescent region between the 2023 Mw 7.8 Nurdağı-Pazarcık earthquake and the 2020 Mw 6.8 Elazığ earthquake is released aseismically through afterslip, indicating that it may be characterized by the rate-strengthening property (Guo et al., 2020; Yue et al., 2017). We thus argue that the possibility of a strong earthquake in this region in the near future is low.\n2. We further find that aftershocks are mainly concentrated in regions with positive stress changes induced by afterslip rather than mainshocks. We identify two areas with a substantial increase of Coulomb stress, suggesting a potential for strong aftershocks.\n3. The stress increase due to the coseismic slip exceeds 0.03 bar on the DSFZ, pushing the fault closer to failure. Additionally, the increased Coulomb stresses from the coseismic slip and afterslip affect northern faults, including the Gerger fault, the Malatya fault, the Narince fault, and the Pürtürge segment. Therefore, the seismic potential of these faults requires close attention.\nTo make a clearer statement on these findings and their benefits, we have added more discussion in the revision.\nReferences:\nAvouac, J.-P. From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle. Annu. Rev. Earth Planet. Sci.43, 233-271 (2015).\nChurchill, R. M., Werner, M. J., Biggs, J. & Fagereng, Å. Afterslip Moment Scaling and Variability From a Global Compilation of Estimates. Journal of Geophysical Research: Solid Earth127, e2021JB023897 (2022).\nChurchill, R. M., Werner, M. J., Biggs, J. & Fagereng, Å. Spatial Relationships Between Coseismic Slip, Aseismic Afterslip, and On-Fault Aftershock Density in Continental Earthquakes. Journal of Geophysical Research: Solid Earth129, e2023JB027168 (2024).\nGuo, R., Zheng, Y. & Xu, J. Stress modulation of the seismic gap between the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake and implications for seismic hazard. Geophysical Journal International221, 2113–2125 (2020).\nHillers, G., Ben-Zion, Y. & Mai, P. M. Seismicity on a fault controlled by rate- and state-dependent friction with spatial variations of the critical slip distance. Journal of Geophysical Research: Solid Earth111, (2006).\nLay, T., andH. Kanamori(1981),An asperity model of large earthquake sequences,Earthq. Predict.,4,579–592.\nLay, T.,H. Kanamori, andL. J. Ruff(1982),The asperity model and the nature of large subduction zone earthquakes,Earthquake Predict. Res.,1982(1),3–71.\nPousse-Beltran, L. et al. The 2020 Mw6.8 Elazığ (Turkey) Earthquake Reveals Rupture Behavior of the East Anatolian Fault. Geophys. Res. Lett.47, e2020GL088136 (2020).\nScholz, C. H.(1998),Earthquakes and friction laws,Nature,391(6662),37–42, doi:10.1038/34097.\nYue, H. et al. The 2016 Kumamoto Mw = 7.0 Earthquake: A Significant Event in a Fault–Volcano System. Journal of Geophysical Research: Solid Earth122, 9166–9183 (2017).\nZhao, B. et al. Aseismic slip and recent ruptures of persistent asperities along the Alaska-Aleutian subduction zone. Nat Commun13, 3098 (2022).\nReviewer #2 (Remarks to the Author):\nI enjoyed reading this InSAR-based analysis of the 2023 SE Turkey earthquake sequence, which to my knowledge is the first such study to focus on observations and mechanisms of triggered post-seismic afterslip and aftershocks. The key results are (1) that afterslip concentrates around the edges of coseismic slip asperities, and (2) that afterslip and aftershocks are closely linked both spatially and temporally, implying that aftershocks result from failure of small asperities loaded by the afterslip. These results are not entirely surprising, but this sequence provides one of the best datasets constraining these relations anywhere in the world, so the results are certainly significant to the field. The paper is well written and illustrated, and mostly well referenced (with a few exceptions, detailed below), and so I would urge publication following some minor revisions.\nResponse: Thanks for your summary of the paper, and we appreciate your thorough and constructive comments!\nMy detailed suggestions for revisions are provided as comments or edits in the attached PDF. The most important of these are further emphasized below.\nResponse: Thanks for your suggestion. We have revised the manuscript following your detailed suggestions.\n1) There is little emphasis on what was known about the EAF before 2023. In particular, I’d draw your attention to the calibrated, relocated seismicity presented by Pousse-Beltran et al. (2020), GRL,https://doi.org/10.1029/2020GL088136.Their Figure S9 shows that background seismicity extends to 18-20 km depth all along the EAF, which is significantly deeper than the 2-12 km range you cite in Line 293 (you do not reference this sentence, so I’m not sure where you get this range from). Note that Pousse-Beltran’s calibrated, multi-event relocated depths are far more reliable than single-event locations derived from routine catalogs.\nResponse: Thanks for your suggestion.\n1．Our original analysis of the background seismicity is from the catalog provided by Tan (2021). The focal depths of the background events range from 0-22 km with a peak at 2-12 km.\n2．To be clearer and more reliable, we have updated Fig. 5e using the relocated seismicity from Pousse-Beltran et al. (2020).\n3．We have revised it in the revision as follows:\n“We find that the relocated background earthquakes along the EAFZ (Pousse-Beltran et al., 2020) are active within a depth range of 4-22 km, consistent with the dominant depth range of aftershocks. Additionally, most of the aftershocks (Ding et al., 2023) are concentrated between the coseismic asperity and postseismic afterslip.”\nYou might also be interested to note Pousse-Beltran’s (2020) relocation of a pair of M 6 earthquakes in 1986 to along the Surgu fault. This may explain why you see a lack of slip along this fault in your coseismic models (Line 225).\nResponse: Thanks for your suggestion. To be clearer, we have added this possible reason in the revision, as follows:\n“Results show that SF is characterized by a small slip, possibly due to the 1986 M ~6 earthquake sequence that occurred along this fault (Pousse-Beltran et al., 2020; Tan, 2021; Taymaz et al., 1991).”\nSimilarly, the seismic gap between the 2023 and 2020 earthquakes, in which you observe much afterslip, is also the location of two large historical earthquakes, in 1893 and 1905. These are plotted in Figure 1 of Pousse-Beltran et al. (2020), and the original reference for these is Ambraseys (1989), GJI,https://doi.org/10.1111/j.1365-246X.1989.tb04453.x.This part of the fault may have had some afterslip following the 2020 earthquake (check Cakir et al. 2023, which you already cite). Both of these things should be noted.\nResponse: Thanks for your suggestion.\n1．Here, we just know that the 2 March 1893 (M ~7.1) and 4 December 1905 (Ms 6.8) Malatya earthquakes were both centered on the Yarpuzlu restraining bend, with damage focused upon settlements between Erkenek (in the west) and Pütürge (in the east) (Ambraseys, 1989). Without more precise information on the fault extents of the 1893 and 1905 earthquakes (Pousse-Beltran et al., 2020), it is unclear whether they ruptured the seismically quiescent region (SQR) between the 2023 and 2020 earthquakes, preventing us from further characterizing its slip behavior and frictional property.\n2．The afterslip (~10 km along strike) to the west of the coseismic slip area associated with the 2020 Mw 6.8 Elazığ earthquake is in fact coseismic slip of the largest aftershock (Mw 5.6) that took place on August 4, 2020 (Cakir et al. 2023). It is not included in the SQR. To show the SQR between the 2023 and 2020 earthquakes more clearly, we have added Fig. 1h in the revision.\n3．We have conducted further discussions based on your suggestions, as detailed below:\n“The Mw 7.8 Nurdağı-Pazarcık earthquake ruptured ~300 km along the western EAFZ. This event occurred just 3 years after the devastating 2020 Mw 6.8 Elazığ earthquake that ruptured the central segment of EAFZ, leaving a ~40-km seismically quiescent region (SQR) (Fig. 1h). Notably, the aftershock distribution connects these two events below ~10 km, thus SQR is located between the surface and 10 km depth.Our optimal afterslip model suggests that the accumulated energy within the SQR is released aseismically through afterslip (Fig. 2d), resulting in a stress shadow (Fig. 5b). It indicates that the SQR may be characterized by the rate-strengthening property (Guo et al., 2020; Yue et al., 2017), preventing the coseismic rupture of the 2023 Mw 7.8 Nurdağı-Pazarcık earthquake and the 2020 Mw 6.8 Elazığ earthquake. Consequently, the likelihood of a strong earthquake occurring in this region in the near future is low. It is necessary to mention that the 1893 M ~7.1 and 1905 Ms 6.8 Malatya earthquakes occurred near the SQR (Ambraseys, 1989). However, in the absence of more precise information on the extent of faulting for the 1893 and 1905 events (Pousse-Beltran et al., 2020), it is unclear whether these two earthquakes ever ruptured the SQR, preventing us from further characterizing its slip behavior and frictional property.”\n2) In your analysis of the relationship between afterslip and aftershocks, you seem to assume that the latter all occur on the mainshock slip planes (or their direct continuations down-dip or along strike). But is this really the case? My understanding is that many of the aftershocks occurred some distance (perhaps up to several kilometers) away from the main fault plane. If this is the case, then I think that this should be discussed somewhere in the Section titled “Interplay between afterslip and aftershocks”.\nResponse: Thanks for your suggestion. Yes, there are indeed some aftershocks that occurred away from the main fault plane. To discuss the interplay between aftershocks and afterslip more robustly, we carried out different aftershock selections for different issues. The details are as follows:\n1.To investigate the spatial and triggering relationship between aftershocks and afterslip on the fault planes, we selected “near-fault” aftershocks within 5 km of the seismogenic faults following the strategy of Churchill et al. (2024) (Fig. 5b).\n2.To further discuss the triggering relationship between afterslip and aftershocks at a distance from the main fault planes, we have calculated the stress change map at the depth of 10 km. Here, we selected aftershocks in the depth interval of 10±3 km (Fig. 7d).\n3.To decipher the temporal decay pattern of aftershocks and that of afterslip, and compare the seismic moment released by aftershocks to the geodetically derived postseismic moment, we selected all aftershocks above the completeness magnitude following the strategy of Zhao et al. (2022) (Figs. 6c and 6d).\nIn addition, we have specified the principles of aftershock selection and added the related discussion in the revision.\n3) Most of the figures look nice but I find the colouring on Figure 5 garish, making it hard to distinguish the purple aftershocks from the red-blue CFS colour maps. I suggest muting the CFS colours, and perhaps changing the aftershocks from purple to black to let them stand out more.\nResponse: Thanks for your suggestion. We have redrawn it in the revision.\n4) I’d prefer you to name faults that are part of the main, through-going East Anatolian Fault as “segments” rather than their own faults. You will therefore need to alter many of the acronyms given at the end of the Figure 1 caption. Your inset to Figure 1 implies a major plate boundary between the Aegean Sea and the Anatolia plate, where there is none. The Aegean is simply the rifted part of the western Anatolian plate, where this comes under the influence of the Hellenic trench.\nResponse: Thanks for your suggestion. We have modified them in the revision.\nHere are the specific suggestions in the attached PDF:\n1. Line 1. Is there a title that explains what you found, not what you did?\nResponse: Thanks for your suggestion. In this work, we integrate InSAR and strong-motion observations to investigate the interplay between the coseismic rupture, postseismic afterslip, and aftershocks associated with the 2023 Kahramanmaraş double. The significance of our results is threefold:\n1．The multi-fault coseismic rupture and ~4-month postseismic afterslip of the 2023 Kahramanmaraş double, as well as the slip distributions of two strong aftershocks with Mw>6.0, are revealed. Both strong aftershocks occurred on subparallel and seismically active branches, suggesting a complex fault system.\n2．We develop a combined afterslip model that incorporates both kinematic shallow afterslip and stress-driven deep afterslip, which suggests that aseismic afterslip reveals a complementary pattern with coseismic high-slip zones and aftershocks. And afterslip releases 10% of the coseismic moment, consistent with the near-linear scaling of the afterslip moment with the coseismic moment.\n3．Aftershocks are concentrated in regions with positive Coulomb failure stress changes due to afterslip and follow a similar temporal decay as that of afterslip, indicating that aftershock production is the failure of small asperities loaded by afterslip. And the early postseismic afterslip is accommodated 93.2% aseismically and ~6.8% seismically by aftershocks.\nOverall, a simple title may not be a good indication of what we have discovered. In addition, we indeed explore the spatial relationship and moment comparison between coseismic slip, aseismic afterslip, and aftershocks. Therefore, please understand that we did not choose to change the title.\n2. Line 21-23. Strong motion data are only used for one aftershock, so it's misleading to place it here (since it infers you use strong motion data for the two mainshocks).\nResponse: Thanks for your suggestion. We have revised it, as follows:\n“Here, we utilize InSAR data to derive the coseismic rupture during the doublet, ~4-month postseismic afterslip, and, with the addition of strong motion data, slip distributions of two Mw>6.0 aftershocks.”\n3. Line 36. Add Duman and Emre (2013)? This is a great review paper that details and summarizes many aspects of the EAF.\nResponse: Thanks for your suggestion. We have added this citation in the revision.\n4. Line 37. This is incorrect: the EAF marks the boundary of the Arabian and Anatolian plates, not Arabia and Eurasia.\nResponse: Thanks for your suggestion. We have modified it in the revision.\n5. Line 41. Replace \"fault\" with \"segment\".\nResponse: Thanks for your suggestion. We have modified it in the revision.\n6. Line 42. Define long. Do you mean seismic quiescence? When was the last time this section ruptured?\nResponse: Thanks for your suggestion. We have modified it in the revision as follows:\n“The fault section of the EAFZ stretching from the Erkenek segment (ES) to the Amanos segment (AS) is characterized by a seismic recurrence interval of hundreds to millennia (Duman & Emre, 2013)”\n7. Line 43. This is the wrong reference for a low seismicity rate. I would include Tan (2021) (your reference #28) as well as Pousse-Beltran et al. (2020), GRL, instead. As well as their InSAR model of the 2020 earthquake, Pousse-Beltran relocated seismicity along the full length of the EAF back to the 1960s. One of their supplementary figures clearly shows a lack of seismicity along the segments that ruptured in 2023.\nResponse: Thanks for your suggestion. We have revised the citations.\n8. Line 46. Add Pousse-Beltran et al. (2020), GRL - this was the first paper on the 2020 earthquake and is the model referenced by Barbot's study of the 2023 earthquakes.\nResponse: Thanks for your suggestion. We have added this citation and moved this sentence to the Section “Future seismic potential” in the revision.\n9. Line 74. With small green dots marking segment boundaries?\nResponse: Thanks for your suggestion. We have revised it, as follows:\n“Black lines represent the mapped fault traces with small green dots marking segment boundaries.”\n10. Line 84. The Aegean Sea (and Greece) is really just the rifting part of the Anatolian plate. There is no plate boundary between them, as indicated here. I would remove this line from the inset, and remove reference to the Aegean.\nResponse: Thanks for your suggestion. We have removed it.\n11. Line 86-87. Many of these should be referred to as segments of the EAF, not individual faults.\nResponse: Thanks for your suggestion. We have revised them.\n12. Line 94-95. I appreciate that the methods are described in full in \"Methods\", but I think you should state here that you assumed a fixed fault geometry based on the surface trace and aftershock distribution, and then solved for the slip distribution across that fixed fault geometry.\nResponse: Thanks for your suggestion. In accordance with journal requirements as well as clarity of organization, we have moved all technical details to the supplementary “Methods”.\n13. Line 98. Is this in agreement with other estimates of the seismogenic layer thickness or seismicity cut-off depth? You could check the relocated hypocenter depth histograms of Pousse-Beltran et al. (2020) for background seismicity, and newer papers for the 2023 aftershock distributions.\nResponse: Thanks for your suggestion.\n1.The depth limit of coseismic high-slip zones does coincide with the average seismogenic thickness. We have added this description and related citation in the revision as follows,\n“Fig. 2a and Supplementary Fig. 3a reveal that the majority of coseismic slip is confined to depths above 15-20 km, consistent with the average seismogenic thickness (Güvercin et al., 2022)”\n2.In addition, we have added the related discussion in the later Section “Interplay between afterslip and aftershocks” as follows,\n“We find that the relocated background earthquakes along the EAFZ are active within a depth range of 4-22 km (Pousse-Beltran et al., 2020), consistent with the dominant depth range of aftershocks. Additionally, most of the aftershocks (Ding et al., 2023) are concentrated between the coseismic asperity and postseismic afterslip. Spatially, there exists a complementary distribution among coseismic slip, afterslip, and aftershocks, collectively releasing the accumulated energy.”\n14. Line 99. Normal or reverse? did you solve for dip angle? In previous work on the EAF, it's been suggested that it dips steeply north-westwards.\nResponse: Thanks for your suggestion.\n1.The slip distribution exhibits significant spatial heterogeneity, characterized by predominant strike-slip motion with minor occurrences of normal or thrust faulting, consistent with previous results (e.g., He et al., 2023; Liu et al., 2023). We have stated it in the revision as follows,\n“The 2023 Kahramanmaraş earthquake doublet is dominated by sinistral slip, accompanied by minor normal or reverse components, which is consistent with previous studies (e.g., He et al., 2023; Liu et al., 2023).”\n2. The dip angles are established based on the work of Jia et al. (2023) (Supplementary Table 4). In addition, the detailed analyses of the relocated aftershocks also indicate that the EAF features a near-vertical fault dip (Ding et al., 2023).\n15. Line 100. “solution” to “solutions”. Add “catalog”.\nResponse: Thanks for your suggestion. We have deleted this sentence in the revision.\n16. Line 120-121. Which slip model of the 2020 earthquake are you using to measure this gap length?\nResponse: Thanks for your suggestion.\n1. We applied the slip model of the 2020 earthquake from Pousse-Beltran et al. (2020)to measure its length following the strategy of Barbot et al. (2023).\n2. To enhance readability and understanding, we have added Figure 1h to describe theseismically quiescent region.\n17. Line 138. highest?\nResponse: Thanks for your suggestion.\n1. As shown in Fig. 2b, a significant afterslip is located on the ÇF.\n2. To clarify, we have revised it in the revision. A similar usage can be found in Bedford et al. (2013) and Jiang et al. (2018).\n“Notably, the high-afterslip concentration zone is located on the ÇF, with a maximum slip of ~0.65 m at a depth of ~16 km.”\n18. Line 140. a moment magnitude of 7.3. (It's not really equivalent to \"an event\", since it's spread out so widely).\nResponse: Thank you for your suggestion. We have modified it in the revision.\n19. Line 199. This seems quite deep considering your results for the doublet, as well as background seismicity (see e.g. relocated focal depth histograms of Pousse-Beltran et al. 2020)\nResponse: Thanks for your suggestion.\n1. The high-slip region (8-24 km) of the 06/02/2023 aftershock aligns with the depth range (4-22 km) of the relocated background seismicity along the East Anatolian fault from Pousse-Beltran et al. (2020) (Fig. 5e).\n2. The relocated aftershocks following the Kahramanmaraş earthquake doublet indicate the potential extension of aftershocks to depths ranging from 20-30 km (Ding et al., 2023, Figs. 5f-5g).\n3. The high-slip zone of the 06/02/2023 aftershock is concentrated within the depth range of 8-24 km, spatially complementing the shallow coseismic slip of the Kahramanmaraş earthquake doublet.\nTherefore, the depth range of the high-slip zone associated with the 06/02/2023 aftershock seems reasonable.\n20. Line 219. \"is generally in close agreement\" might be a better choice of phrase.\nResponse: Thanks for your suggestion. We have modified it in the revision.\n21. Line 221-222. Replace “less than” to “above”.\nResponse: Thanks for your suggestion. We have modified it in the revision.\n22. Line 224-225. This is a bit unclear. Given that the Mw 7.7 earthquake ruptured to the surface, you'd expect that the models agree on its surface trace. Do you mean that your model has a different dip angle for the SF? In which case, can you elaborate? By \"align with the local structure\", do you really mean the aftershock distribution?\nResponse: We apologize for not being clear here. To express more clearly, we have rewritten it in the revision as follows,\n“For example, previous models did not consider the contribution of the Sürgü fault (SF) due to the lack of significant displacement discontinuities (He et al., 2023; Ren et al., 2024) and few aftershocks (Ding et al., 2023) near the SF. To align with the local fault structure (Duman & Emre, 2013; Emre et al., 2018), the SF is added to our coseismic model.”\n23. Line 225. If you look carefully at Pousse-Beltran et al. (2020)'s relocation results (Fig. 1, Fig. S9), you'll see that there was a pair of M ~6 earthquakes in 1986 (modelled by Taymaz et al. 1991) along this fault. Perhaps that explains the lack of slip here?\nResponse: Thank you for your suggestion. To be clearer, we have added the discussion in the revision as follows,\n“Results show that SF is characterized by a small slip, possibly due to the 1986 M ~6 earthquake sequence that occurred along this fault (Pousse-Beltran et al., 2020; Tan, 2021; Taymaz et al., 1991).”\n24. Line 263. I find that the purple seismicity is hard to distinguish given the vivid colours of stress change. Could you \"mute\" the stress change colour scale to better highlight the seismicity?\nResponse: Thanks for your suggestion. We have redrawn it in the revision.\n25. Line 269. From which source? Note that routine catalog depths may not be accurate.\nResponse: Thanks for your suggestion. We have redrawn it based on the relocated background seismicity from Pousse-Beltran et al. (2020) and cited this paper in the revision.\n26. Line 274-275. This assumes that the aftershocks lie on the main fault plane. Is this true? Weren't many of the aftershocks some distance away from the main fault plane? This would be good to discuss.\nResponse: Thanks for your suggestion. There are indeed some aftershocks that occurred away from the main fault plane. To better investigate the triggering relationship between aftershocks and afterslip, we discuss it separately on the fault plane and at the depth of the mainshock hypocenter.\n1．To decipher the triggering relationship between aftershocks and afterslip on the fault plane, we selected “near-fault” aftershocks within 5 km of the seismogenic faults following the strategy of Churchill et al. (2024) (Fig. 5b).\n2．In addition, we have calculated the stress change map at the depth of 10 km to further discuss the triggering relationship between afterslip and aftershocks at a distance from the main fault planes (Fig. 7d). Here, we selected aftershocks in the depth interval of 10±3 km.\nIn addition, we have specified the principles of aftershock selection and added related discussion in Sections “Interplay between afterslip and aftershocks” and “Future seismic potential” in the revision.\n27. Line 292-293. Look at the depth histograms in Pousse-Beltran et al. (2020), Figure S9. These multi-event relocated focal depths are much more reliable than single-event catalog depths. You will find that the background seismicity cut-off depth is about 18-20 km depth in the EAF region.\nResponse: Thanks for your suggestion. To be clearer and more reliable, we have updated Fig. 5e using the relocated background seismicity fromPousse-Beltran et al. (2020). In addition, we have revised the description in the revision as follows,\n“We find that the relocated background earthquakes along the EAFZ are active within a depth range of 4-22 km (Pousse-Beltran et al., 2020), consistent with the dominant depth range of aftershocks. Additionally, most of the aftershocks (Ding et al., 2023) are concentrated between the coseismic asperity and postseismic afterslip.”\n28. Line 310. Replace “the larger depths” with “greater depth”.\nResponse: Thanks for your suggestion. We have modified it in the revision.\n29. Line 324. How much? Note that this section ruptured in historical earthquakes in 1893 and 1905 (Ambraseys, 1989, GJI).\nResponse: Thanks for your suggestion. To be clearer, we have added related discussion in the revision as follows:\n“Our optimal afterslip model suggests that the accumulated energy within the SQR is released aseismically through afterslip (Fig. 2d), resulting in a stress shadow (Fig. 5b). Consequently, the possibility of a strong earthquake in this region in the near future is low. In addition, it is necessary to mention that the 1893 M ~7.1 and 1905 Ms 6.8 Malatya earthquakes occurred near the SQR (Ambraseys, 1989). However, in the absence of more precise information on the extent of faulting for the 1893 and 1905 events (Pousse-Beltran et al., 2020), it is unclear whether these two earthquakes ever ruptured the SQR, preventing us from further characterizing its slip behavior and frictional property.”\n30. Line 337. I would prefer \"raised likelihood\". \"Great\" is too alarmist; there are numerous examples of CFS models that highlight supposed future earthquakes that never come to pass.\nResponse: Thanks for your suggestion. We have modified it as follows,\n“Given the significantly increased CFS on the DSFZ due to the Kahramanmaraş doublet and the fact that the DSFZ is highly coupled (Özkan et al., 2023), it has the potential to generate strong earthquakes and derives more attention.”\nReferences:\nAktug, B. et al. Slip rates and seismic potential on the East Anatolian Fault System using an improved GPS velocity field. J. Geodyn.94-95, 1-12 (2016).\nAmbraseys, N. N. Temporary seismic quiescence: SE Turkey. Geophysical Journal International 96, 311–331 (1989).\nBarbot, S. et al. Slip distribution of the February 6, 2023 Mw 7.8 and Mw 7.6, Kahramanmaraş, Turkey earthquake sequence in the East Anatolian Fault Zone. Seismica2 (2023).\nBedford, J. et al. A high-resolution, time-variable afterslip model for the 2010 Maule Mw = 8.8, Chile megathrust earthquake. Earth and Planetary Science Letters383, 26-36 (2013).\nBletery, Q., Cavalié, O., Nocquet, J.-M. & Ragon, T. Distribution of Interseismic Coupling Along the North and East Anatolian Faults Inferred From InSAR and GPS Data. Geophys. Res. Lett. 47, e2020GL087775 (2020).\nCakir, Z. et al. Arrest of the Mw 6.8 January 24, 2020 Elaziğ (Turkey) earthquake by shallow fault creep. Earth and Planetary Science Letters608, 118085 (2023).\nChurchill, R. M., Werner, M. J., Biggs, J. & Fagereng, Å. Spatial Relationships Between Coseismic Slip, Aseismic Afterslip, and On-Fault Aftershock Density in Continental Earthquakes. Journal of Geophysical Research: Solid Earth129, e2023JB027168 (2024).\nDing, H. et al. High-resolution seismicity imaging and early aftershock migration of the 2023 Kahramanmaraş (SE Türkiye) MW7.9 & 7.8 earthquake doublet. Earthquake Science36, 417–432 (2023).\nDuman, T. Y. & Emre, Ö. The East Anatolian Fault: geometry, segmentation and jog characteristics. in Geological Development of Anatolia and the Easternmost Mediterranean Region (eds. Robertson, A. H. F., Parlak, O. & Ünlügenç, U. C.) vol. 372 0 (Geological Society of London, 2013).\nEmre, Ö. et al. Active fault database of Turkey. Bull Earthquake Eng16, 3229–3275 (2018).\nGüvercin, S. E., Karabulut, H., Konca, A. Ö., Doğan, U. & Ergintav, S. Active seismotectonics of the East Anatolian Fault. Geophys. J. Int.230, 50-69 (2022).\nGuo, R., Zheng, Y. & Xu, J. Stress modulation of the seismic gap between the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake and implications for seismic hazard. Geophysical Journal International221, 2113–2125 (2020).\nHamiel, Y. & Piatibratova, O. Spatial Variations of Slip and Creep Rates Along the Southern and Central Dead Sea Fault and the Carmel–Gilboa Fault System. J. Geophys. Res.: Solid Earth 126, e2020JB021585 (2021).\nHe, L. et al. Coseismic Kinematics of the 2023 Kahramanmaras, Turkey Earthquake Sequence From InSAR and Optical Data. Geophysical Research Letters50, e2023GL104693 (2023).\nJia, Z. et al. The complex dynamics of the 2023 Kahramanmaraş, Turkey, Mw 7.8-7.7 earthquake doublet. Science 381, 985-990 (2023).\nJiang, Z., Yuan, L., Huang, D., Yang, Z. & Hassan, A. Postseismic deformation associated with the 2015 Mw 7.8 Gorkha earthquake, Nepal: Investigating ongoing afterslip and constraining crustal rheology. J. Asian Earth Sci.156, 1-10 (2018).\nMahmoud, Y. et al. Kinematic study at the junction of the East Anatolian fault and the Dead Sea fault from GPS measurements. J. Geodyn.67, 30-39 (2013).\nÖzkan, A., Yavaşoğlu, H. H. & Masson, F. Present-day strain accumulations and fault kinematics at the Hatay Triple Junction using new geodetic constraints. Tectonophysics854, 229819 (2023).\nPousse-Beltran, L. et al. The 2020 Mw6.8 Elazığ (Turkey) Earthquake Reveals Rupture Behavior of the East Anatolian Fault. Geophys. Res. Lett.47, e2020GL088136 (2020).\nRen, C. et al. Supershear triggering and cascading fault ruptures of the 2023 Kahramanmaraş, Türkiye, earthquake doublet. Science383, 305–311 (2024).\nTan, O. A homogeneous earthquake catalogue for Turkey. Nat. Hazards Earth Syst. Sci. 21, 2059-2073 (2021).\nTaymaz, T., Eyidog̃an, H. & Jackson, J. Source parameters of large earthquakes in the East Anatolian Fault Zone (Turkey). Geophysical Journal International106, 537–550 (1991).\nWang, R. et al. The 2011 Mw 9.0 Tohoku Earthquake: Comparison of GPS and Strong‐Motion Data. Bull. Seismol. Soc. Am. 103, 1336-1347 (2013).\nYue, H. et al. The 2016 Kumamoto Mw = 7.0 Earthquake: A Significant Event in a Fault–Volcano System. Journal of Geophysical Research: Solid Earth122, 9166–9183 (2017).\nZhao, B. et al. Aseismic slip and recent ruptures of persistent asperities along the Alaska-Aleutian subduction zone. Nat Commun13, 3098 (2022).\nReviewer #3 (Remarks to the Author):\nThis manuscript presents observations and modeling of co-seismic and early post-seismic deformation due to a pair of major strike-slip earthquakes that occurred in southern Turkey last year. The authors use InSAR data to constrain finite fault models (FFMs) of coseismic slip and afterslip that occurred over a time period of 4 months after the events. They find that the observed post-seismic deformation is consistent with afterslip occurring at the periphery of high co-seismic slip areas (\"seismic asperities\"). The authors quantify the relative magnitudes of the co-seismic slip and afterslip, as well as the relative contributions of afterslip and aftershocks to the observed post-seismic deformation. They find that the moment release due to afterslip is a small fraction of the moment release due to the mainshock(s), and the moment release due to aftershocks is a small fraction of that due to afterslip. The authors also find that the co- and post-seismic slip on faults ruptured during the 2023 sequence have a complementary spatial pattern, as observed for many previous earthquakes. Finally, the authors derive slip models for two strong aftershocks, and calculate static stress changes on faults adjacent to the earthquake ruptures. The manuscript is generally well written, and the results appear to be technically sound. There have been a number of studies of the 2023 Turkey doublet, which is understandable given the earthquake size and impact. This study focuses on the interplay between seismic and postseismic processes, and presents some new (postseismic) data and interpretation that may be of interest to a broader community. I am happy to recommend publication in Nature Communications pending a moderate revision (mostly of editorial nature to improve the manuscript readability). My comments below are ordered by the line numbers, not by significance.\nResponse: Thanks for your suggestion. We have revised the manuscript according to your detailed comments.\n1. line 19. \"... of faults\" (plural)\nResponse: Thanks for your suggestion. We have modified it in the revision.\n2. line 23. \"this doublet\" - it's not clear whether \"doublet\" refers to the two mainshocks, or two aftershocks mentioned in the previous sentence. Please clarify, \"the 2023 Mw 7.8-7.7 doublet...\"\nResponse: Thanks for your suggestion. We have clarified it in the revision.\n3. line 27. Replace \"It\" with \"Afterslip\".\nResponse: Thanks for your suggestion. We have replaced it in the revision.\n4. line 28. \"consistent with the near-linearly coseismic and afterslip moment scale\"- I'm not sure what the authors with to say here. Grammatically, it should be \"near-linear ... scale\" (or scaling). Semantically, I don't see how the fraction of 10% signifies a linear scaling between coseismic slip and afterslip. Please elaborate.\nResponse: Thanks for your suggestion.\n1. We compiled 62 afterslip models following the Mw 6.0–9.1 earthquakes, and found that the afterslip and coseismic moment scale approximately linearly, with a gradient close to one. So, we want to express that afterslip releases ~10% of the coseismic moment, obeying the near-linear scaling of the afterslip moment with the coseismic moment.\n2. We have modified this sentence in the revision as follows,\n“Afterslip releases ~10% of the coseismic moment, obeying the near-linear scaling between the afterslip moment and the coseismic moment.”\n5. line 30. \"follow a similar temporal decay as afterslip\" -> \"follow a temporal decay similar to that of afterslip\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n6. lines 45, 322. The 40 kilometer \"gap\" between the two earthquake ruptures is a controversial item. Some previous studies suggested it, while others did not. The data used in the manuscript have very limited coverage of the eastern tip of the M7.8 rupture to resolve this issue. I suggest removing the mention of this \"gap\" throughout the manuscript, or use additional data to better resolve it.\nResponse: Thanks for your suggestion.\n1.To make the expression more robust, we have replaced the “seismic gap” with “seismically quiescent region”.\n2. To enhance readability and understanding, we have added a subplot Fig. 1h to depict the seismically quiescent region.\n7. line 54. \"are\" -> \"were\" (work done in previous studies)\nResponse: Thanks for your suggestion. We have modified it in the revision.\n8. line 58. \"on the smaller event\" -> \"on the hypocentral region of the 2nd mainshock\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n9. line 65. \"to invert the coseismic fault slip\" -> \"to invert for the coseismic fault slip\" (one inverts the data for the model parameters).\nResponse: Thanks for your suggestion. We have modified it in the revision.\n10. line 72. \"Seismicity and data used in this study\" -> \"Seismicity and InSAR data used in this study\".\nResponse: Thanks for your suggestion. Because this panel also includes the strong-motion data, we don’t modify it.\n11. line 73. InSAR frames and labels can be hardly seen in panel 1a - please use more contrasting colors.\nResponse: Thanks for your suggestion. The lines of InSAR frames have been thickened to make them clearer.\n12. line 90. \"Coseismic deformation of the 2023 Kahramanmaraş earthquake doublet is mapped well by...\" -> \"Coseismic deformation due to the 2023 Kahramanmaraş earthquake doublet is well mapped by...\"\nResponse: Thanks for your suggestion. We have removed it for clarity in the revision.\n13. line 124. \"We collect a total of...\" -> \"We use a total of...\" (data were collected by a satellite, not by the authors).\nResponse: Thanks for your suggestion. We have removed it for clarity in the revision.\n14. line 128. \"deformation mainly arises from\" -> \"deformation may arise from\"\nResponse: Thanks for your suggestion. We have modified it and moved it to the Supplementary “Methods” in the revision.\n15. line 133. What do the authors mean by \"deformation stability\"? Perhaps \"quasi-steady deformation pattern\"?\nResponse: We apologize for the confusion here. We have modified it and moved it to the Supplementary “Methods” in the revision as follows,\n“Considering the limitations of the Common-Scene-Stacking method in mitigating atmospheric noise in the end images (Wang et al., 2020), we exclude the last few scenes to determine the postseismic deformation.”\n16. line 137. \"coseismic slip is sparse\" -> \"coseismic slip is low\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n17. line 160. \"occurring in the downdip of...\" -> \"occurring downdip of...\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n18. line 218. \"Compared\" -> \"Comparison\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n19. line 219. \"overlaps\" -> \"shares many common features\"\nResponse: Thanks for your suggestion. We have modified it as follows,\n“Our optimal coseismic slip distribution is generally in close agreement with published coseismic rupture models”\n20. line 220. \"because all of us invoke the SAR images...\" -> \"because our study uses the same SAR data as the previous studies\". Delete the rest of the sentence (\"with high spatial resolution during the inversion\").\nResponse: Thanks for your suggestion. We have modified it.\n21. lines 233-235. Panels an and b in Fig. 4 are redundant, as they present the same data. Consider removing one of them. If you keep panel 4a, it would be useful to label the dashed lines \"100%\", \"10%\", \"1%\".\nResponse: Thanks for your suggestion.\n1. We have redrawn it and added the label.\n2. To better understand the afterslip moment scaling, we didn’t remove Fig. 4b. In addition, we further discussed the relationship between the relative afterslip moment (M =Maft /M ) and the corresponding coseismic moment in the revision.\n22. lines 253-254. Complementary patterns of coseismic slip and afterslip was noted in a number of earlier studies, e.g. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JB011122\nResponse: Thanks for your suggestion. We have cited this reference in the revision.\n23. line 323-324. \"the accumulated energy within the seismic gap is released aseismically through afterslip\" - if that is the case, the respective fault segment is velocity-strengthening, and cannot be referred to as \"the seismic gap\".\nResponse: Thanks for your suggestion. We have changed “the seismic gap” to “the seismically quiescent region” in the revision.\n24. line 328. \"on the neighboring major fault\" -> \"on neighboring major faults\"\n(the authors compute stress changes on several faults, not some specified fault).\nResponse: Thanks for your suggestion. To prevent duplication with the previous description, we have removed this section in the revision.\n25. line 337-338. \"Given the DSFZ is highly coupled, it has a great likelihood of strong earthquakes in the near future, deriving more attention\" - this is an overstatement. The static Coulomb stress increase does not imply that a future rupture is imminent. Please rephrase or remove.\nResponse: Thanks for your suggestion. We have rephrased it in the revision as follows,\n“The results reveal that the stress increase due to the coseismic slip exceeds 0.03 bar on the DSFZ, bringing the fault closer to failure, while afterslip has little effect on the DSFZ, being smaller than 0.01 bar. Given the significantly increased CFS on the DSFZ due to the Kahramanmaraş doublet and the fact that the DSFZ is highly coupled (Özkan et al., 2023), it has the potential to generate strong earthquakes and derives more attention.”\n26. line 363. \"facilitates the reduction of the phase gradient\" -> \"results in a better phase coherence\"\nResponse: Thanks for your suggestion. We have modified it in the revision.\n27.line 364. \"additionally add\" -> \"additionally use\".\nResponse: Thanks for your suggestion. We have modified it in the revision.\nReferences:\nÖzkan, A., Yavaşoğlu, H. H. & Masson, F. Present-day strain accumulations and fault kinematics at the Hatay Triple Junction using new geodetic constraints. Tectonophysics854, 229819 (2023).\nWang, K. & Bürgmann, R. Probing Fault Frictional Properties During Afterslip Updip and Downdip of the 2017 Mw 7.3 Sarpol-e Zahab Earthquake With Space Geodesy. J. Geophys. Res.: Solid Earth125, e2020JB020319 (2020)."}, {"round": 2, "reviewer_comments": {"reviewer_4": "I find the study to be timely and of publishable quality. The authors have addressed all the comments from the previous reviewers in the revised manuscript. However, I have some concerns about the interpretations based on the seismic characteristics of the East Anatolian Fault Zone (EAFZ). The authors reference Pousse-Beltran et al. (2020) and Ding et al. (2023). I suggest that the authors also consider Guvercin (2024), which presents a detailed aftershock catalog with a different depth distribution based on 1D velocity models representing various segments of the EAFZ. Additionally, I recommend that the authors review Konca et al. (2021), which discusses the Pütürge segment and reports the observation of repeating earthquakes. I believe that incorporating these two papers would elevate the discussion to a more sophisticated level.", "reviewer_5": "The authors present a comprehensive analysis of the 2023 Kahramanmaraş earthquake doublet, covering the coseismic slip model, afterslip models, slip distribution of two major aftershocks, and discussions on coseismic and afterslip moment scaling, the interplay between afterslip and aftershocks, fault frictional properties, and earthquake potential. The analysis and results are clearly presented, and the new postseismic analysis will be valuable to the community. However, the manuscript attempts to address too many topics, which results in a lack of clear focus. It feels somewhat like a “fishing expedition,” where the central question or theme remains unclear. While the manuscript contains valuable components, it reads more like a case study report. What’s missing is a discussion on how these findings contribute to broader, more significant questions, such as fault mechanical properties—of which only frictional properties are briefly mentioned.\nThe presentation would also benefit from better organization. For instance, it would be more logical to discuss the coseismic models first, followed by the afterslip models and their interplay. Additionally, the section “Comparison with published coseismic slip models” could be merged with “Coseismic rupture during the Kahramanmaraş doublet” to improve the overall flow.\nL412: The uncertainties associated with the deep slip portion (derived from the stress-driven afterslip model) and the shallow slip portion (from the kinematic inversion) need to be quantified. Additionally, the manuscript should provide details on how these uncertainties were evaluated for the optimal slip model.\nL478-480: Please provide quantitative descriptions of how much the model fit improves.\nL539: Coseismic and Afterslip Moment Scaling:\nThe afterslip moment heavily depends on the observation period. The authors only utilized 4 months of InSAR observations to estimate the afterslip, which likely leads to a significant underestimation of the total postseismic moment. Therefore, the merit of discussing afterslip at this early stage is limited, as the short observational period may not capture the full postseismic deformation. Since the authors are using Unicycle to simulate afterslip, I suggest simulating the afterslip moment release to provide a range of possible estimates. Additionally, uncertainty quantification is necessary for all estimates provided.\nL757-758: “most “near-fault” aftershocks (within a distance of 5 km of the fault plane) fall within the regions of positive caused by afterslip rather than mainshocks.”\nThis statement requires more quantitative support. It would be useful to provide the percentage of aftershocks that occur in positive or negative dCFS changes from coseismic versus postseismic slip. Additionally, including the spatio-temporal relationship between aftershocks and afterslip would strengthen the argument that afterslip drives aftershocks. Providing snapshots of the relative timing would help substantiate this claim.\nL834: More thorough documentation is needed on how the frictional parameters were determined. Did the authors evaluate InSAR time series across all locations, or only focus on the two regions in Fig. 3? This requires clarification. Additionally, how do these findings compare to other earthquakes? Simply reporting a value without context is not particularly informative.\nLines 405-407: “Discrepancies between the kinematic and stress-driven afterslip models may be attributed to heterogeneous frictional parameters on the fault plane”\nDid the authors find evidence of heterogeneous frictional parameters at those specific locations?\nLine 1714: The term \"seismic moment\" in this context should be corrected to \"geodetic moment.\"\nFig 6. What proportion of the afterslip moment is attributed to deep versus shallow afterslip?"}, "author_response": "Response: Thanks for your summary and suggestions.\n1.We have utilized the aftershock catalog from Guvercin (2024) for our analysis in the revision, as it offers a high-resolution, detailed, and comprehensive collection of aftershock data using the updated velocity models and station corrections.\n2.We have utilized the coseismic slip of the 2020 Mw 6.8 Sivrice (Elazığ) earthquake from Konca et al. (2021), as it provides a robust rupture model using strong-motion and teleseismic P and SH waveforms, high-rate GNSS, and static displacements from ascending and descending InSAR pairs and continuous GNSS stations.\n3.In addition, we have added some discussion based on these two papers, which support our argument that the seismically quiescent region between the 2020 Mw 6.8 Sivrice (Elazığ) earthquake and the 2023 Mw 7.8 Nurdağı-Pazarcık earthquake may be characterized by the rate-strengthening property.\nResponse: Thanks for your summary and suggestions.\n1.Seismic and aseismic slip are two main modes of fault behavior, with their spatial distribution shedding some light on the frictional properties of faults and serving as an indicator of seismic potential. The well-recorded 2023 Mw 7.8-Mw 7.7 Kahramanmaraş earthquake doublet provides an excellent opportunity to understand the partitioning of seismic and aseismic fault slip. We thus focus on the interplay between seismic and aseismic slip in this work, as highlighted in the manuscript, such as the title, abstract, and introduction.\n2.Delineating seismic and aseismic slip on faults does require the exploration of different slip modes, including the coseismic slip, afterslip, and aftershocks. These components are integral to understanding how seismic and aseismic processes interact.\n3.The expression of “mechanical properties” may indeed be too broad, and we have modified it to “frictional properties” in the revision.\n4.In addition, we have added more discussion and evidence to support our argument in the revision.\nResponse: Thanks for your suggestions.\n1.We have made the necessary adjustments to improve the overall flow in the revision.\n2.We have merged the section “Comparison with published coseismic slip models” with “Coseismic rupture during the Kahramanmaraş doublet” in the revision.\n3.In addition, we have merged the section “Coseismic and postseismic slip patterns” and the section “Interplay between afterslip and aftershocks” into the section “Interplay between the coseismic slip, afterslip, and aftershocks” in the revision.\nResponse: Thanks for your suggestions. We have added an analysis of model uncertainties in the revision (see “Methods”), following the strategy outlined by Perfettini and Avouac (2007). Given various trade-offs among the model parameters, we have selected models falling within the 68% confidence level and computed the slip uncertainties for each fault patch based on these models. For the optimal afterslip model, the slip uncertainties are smaller than 0.22 m (Supplementary Fig. 13b), demonstrating the robustness of our preferred afterslip model.\nResponse: Thanks for your suggestions. The root-mean-square of residuals of the optimal afterslip model is 13.4 mm, smaller than 14.3 mm yielded by the stress-driven afterslip model. We have added a table in Supplementary Information to describe the misfits of different afterslip models in the revision.\n“As illustrated in Supplementary Fig. 14, the InSAR-observed cumulative postseismic transients are explained well by the combined afterslip model, displaying an improved fit compared to the stress-driven afterslip model (Supplementary Table 1), particularly for the near-field deformation.”\nResponse: Thanks for your suggestions.\n1.Based on 148 afterslip studies, Churchill et al. (2022) have suggested that there is no strong relationship between the afterslip moment and the observation start time and duration. As shown in Fig. 4, our study also reveals a similar argument, indicating the observation period does not significantly affect our findings.\n2.The optimal afterslip model incorporates both the stress-driven deep afterslip and kinematic shallow afterslip. Relying solely on the stress-driven afterslip simulated with Unicycle may lead to an underestimation of the afterslip moment.\n3.Afterslip is aseismic, transient slip that readjusts the fault zone and redistributes stress concentrations following coseismic rupture (Churchill et al., 2022), increasing approximately as a logarithmic function of time (Avouac, 2015; Barbot et al., 2009). Therefore, early postseismic deformation (spanning several months) is effective for investigating the overall characteristics of afterslip following an earthquake.\n4.Most of the afterslip moments for the other earthquakes shown in Fig. 4b are comparable to the time period used in our estimate.\n5.Finally, to support our statement, we have applied Unicycle to simulate the afterslip moment during the first 500 days after the mainshocks. Results reveal that the moment release increases very slowly after ~100 days, with an exponential decay of the increase rate (Fig. R1, left subplot). The moments released within the first 4 months and the first year are of the same order (Fig. R1, left subplot). This intuitively explains why the duration does not significantly affect our findings (Fig. R1, right subplot).\nTherefore, for several reasons mentioned above, we did not choose to utilize the longer-duration afterslip moments derived from Unicycle simulations. Instead, we considered actual afterslip moments following the strategy of Churchill et al. (2022).\nResponse: Thanks for your suggestions.\n1.To provide more quantitative support for our findings, we have calculated the percentages of aftershocks occurring in regions with positive ∆CFS from both coseismic and postseismic slip in the revision.\n“As shown in Fig. 5a, b, the majority of “near-fault” aftershocks29 (within a distance of 5 km of the fault plane) fall within the regions of positive ∆CFScaused by afterslip (~53 %) rather than by the mainshocks (~30 %). This finding is further confirmed by the aftershock catalog from ref. 28, which reveals a higher proportion of aftershocks associated with afterslip (~59%) than with the coseismic slip (~19%).”\n2.We have added snapshots of cumulative aftershocks and afterslip over time in the revision (Supplementary Fig. 16). Since there are no relocated aftershocks available for the same period of the afterslip, we have utilized the relocated aftershocks from Guvercin (2024) along with the aftershock catalog from AFAD. While there may be a large uncertainty in the aftershock locations reported by AFAD, a general observation is that the aftershock hypocenters and afterslip are found to be complementary, strengthening our argument that afterslip mainly drives aftershocks.\nIn addition, we have added the related discussion in the revision.\n“One extreme view of aftershock production is the rupture of small asperities loaded by afterslip, favored by the similar temporal decay between aftershocks and afterslip54. As shown in Fig. 6c, the temporal evolution of the optimal afterslip model correlates well with aftershocks. Moreover, the spatial relationship between aftershocks and afterslip is found to be complementary over time (Supplementary Fig. 16). We thus argue that afterslip may drive the occurrence of aftershocks.”\nResponse: Thanks for your suggestions.\n1.We have added more thorough documentation on how the frictional parameters were determined in the revision. Moreover, to help readers repeat this work, we have shared our model files on Zenodo (https://doi.org/10.5281/zenodo.14223396).\n“Through the trial-and-error approach, the best-fitting stress-driven model is identified, achieving a minimal RMSR of ~14.3 mm. Meanwhile, the optimal values of the frictional parameter and the reference slip rate are determined to be 3 MPa and 1.3 m/yr, respectively (Fig. 3b).”\n2.In this work, we do not directly use the InSAR time series to constrain our afterslip model, yet the observed InSAR time series are still effectively recovered by our stress-driven and optimal afterslip models. To illustrate the effective fits, we focus on two regions: Region B, located near the first mainshock, and Region A, situated near the second mainshock. To clarify it, we have stated in the revision as follows,\n“Herein, although we do not directly use the InSAR time series to constrain the stress-driven afterslip, the predicted time series for Regions A and B are still in good agreement with the observations (Fig. 3a, c, d).”\n3.We have outlined the estimated values from previous studies for comparison with our results, as follows:\n“The stress-driven deep afterslip suggests a uniform frictional parameterabof 3 MPa (Fig. 3b), aligning with the general magnitude order of 10-1-10 MPa derived from afterslip models for other earthquakes45,54,57-60. For instance, a lower bound of 0.7 MPa was identified for the 2004 Mw 6.0 Parkfield earthquake45, and uniform values of 0.42 MPa and 6.5 MPa were determined for the 2020 Mw 7.8 Simeonof Island, Alaska earthquake54 and the 2015 Mw 7.8 Gorkha (Nepal) earthquake60, respectively.”\nResponse: Thanks for your suggestions.\nThe published back-projection results and finite-fault slip models reflect frequency-dependent seismic radiation characteristics, indicating significant heterogeneity across a specific fault segment (e.g., Jia et al., 2023; Zhang et al., 2023). And we have added some related references in the revision.\nResponse: Thanks for your suggestion. We have revised it to “geodetic moment”.\nResponse: Thanks for your suggestion. We have included the detailed proportion of moments released by the deep and shallow afterslip in the manuscript:\n“The total moment yielded by the optimal afterslip model is ~1.2×1020 N·m, with ~88% attributable to the deep afterslip and ~12% to the shallow afterslip.”"}, {"round": 3, "reviewer_comments": {"reviewer_5": "Thank you for taking the time to address my previous feedback. I appreciate the time and effort you invested in clarifying those details and making the necessary adjustments. Everything looks good to me now, and I have no further questions or concerns at this point."}, "author_response": ""}]

Decision letter