The complex dynamics of the 2023 Kahramanmaraş, Turkey, Mw 7.8-7.7 earthquake doublet

Spatial, Temporal, and Dynamic Behavior of Different Entropies in Seismic Activity: The February 2023 Earthquakes in Türkiye and Syria

Türkiye and Syria were hit by two powerful earthquakes on 6 February 2023. A 7.5 magnitude earthquake, soon followed by a second 7.4 magnitude seism, devastated the area. The present study compares three different entropies using data from 2017 to 2023 (55,823 events) in this region and is the first study to use Shannon entropy, Tsallis entropy, and mutability for analyzing the seismic activity in this region. A couple of years before these large earthquakes, both Shannon entropy and mutability show an overall decrease, potentially indicating upcoming large events; however, the detailed results on mutability offer an advantage, as discussed in this paper. A simultaneous overall increase in Tsallis entropy may also point to some kind of warning of the possible occurrence of large events in the area a couple of years later. The three entropies show how they are presently slowly recovering to previous levels in the affected areas. Longer-term studies combining complementary entropies could help to determine regional seismic risk.

The 2023 Mw 7.8-7.7 Kahramanmaraş earthquakes were loosely slip-predictable

Understanding the behavior of large earthquakes over multiple seismic cycles is limited by short time spans of observations compared to recurrence intervals. Most of large instrumentally-recorded earthquakes have occurred on faults lacking well-documented histories of past events. The 2023 Mw 7.8-7.7 Kahramanmaraş earthquake doublet is exceptional as it ruptured multiple segments of the East Anatolian Fault (EAF) system, where historical records of devastating earthquakes span over two millennia. Here, we use historical earthquake records, measurements of interseismic deformation, and published slip models of the 2023 events to evaluate the recurrence patterns of large earthquakes. We compare slip deficit that accrued on each fault segment since the respective penultimate events to the average coseismic slip of the 2023 doublet. We find that the coseismic slip equaled to or exceeded the accumulated slip deficit, suggesting that the slip-predictable recurrence model applies as a lower bound on strain release during the Kahramanmaraş earthquakes.

Extensive off-fault damage around the 2023 Kahramanmaraş earthquake surface ruptures

Quantifying coseismic fault offsets for surface ruptures of major earthquakes is important for earthquake cycle and slip-rate studies, and thus for earthquake hazard assessments. However, measurements of such offsets generally underestimate fault slip due to inelastic deformation and secondary fault offsets, i.e., off-fault damage. Here, we use satellite synthetic aperture radar images to quantify off-fault damage in the two 2023 Kahramanmaraş (Türkiye) magnitude 7.8 and 7.6 earthquakes. We first derive three-dimensional coseismic surface displacements and show that on average ~35% of the coseismic slip is accommodated by off-fault damage within 5-7 km of the coseismic surface ruptures. Fault sections exhibiting geometrical complexities (e.g., bends and step-overs) experienced a higher level of off-fault damage than simpler fault sections. Our results highlight the importance of extending off-fault damage assessments to several km away from fault ruptures and indicate that fault offset measurements may underestimate slip-rate estimations by as much as a third.

Rupture phases reveal geometry-related rupture propagation in a natural earthquake

Understanding and deciphering wiggles from seismograms has been a long endeavor to understand the internal structure of the Earth and to explore earthquake source properties. Here, we make an attempt to decipher the continuous rupture phases as large near-fault velocity pulses along the East Anatolian Fault in the 2023 moment magnitude (Mw) 7.8 Kahramanmaraş, Türkiye, earthquake. Through data analysis and dynamic rupture simulations, we robustly identify the transient supershear rupture on a segment with flat fault trace and rupture deceleration at fault bends. Our study highlights the complexity and superior application of near-fault data for understanding earthquake dynamics.

Seismic versus aseismic slip for the 2023 Kahramanmaraş earthquake doublet

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.

Landscape changes caused by the 2024 Noto Peninsula earthquake in Japan

Landscapes are shaped by tectonic, climatic, and surface processes over geological timescales, but we rarely witness the events of marked landscape change. The moment magnitude 7.5 Noto Peninsula earthquake in central Japan was caused by a large thrust faulting, up to nearly 10 meters of slip, that expanded more than 150 kilometers along the fault zone. The deformation field reconstructed from satellite data and field surveys reveals up to 4.4 meters of uplift and associated coastal advance along the entire northern coast of the peninsula, meter-scale systematic movement of the mountain slopes consistent with slip on flexural faults, and activation of secondary inland faults, suggesting synchronized ruptures. The findings show excellent consistency between the coseismic deformation and geomorphic features and provide a vivid example of the role of a major earthquake in landscape formation.

Unexpected far-field deformation of the 2023 Kahramanmaraş earthquakes revealed by space geodesy

The spatiotemporal pattern of surface displacements from large earthquakes provides crucial insights about the deformation of Earth's crust at various scales and the interactions among tectonic plates. However, the lack of extensive and large-scale geodetic networks near such seismic events hinders our thorough understanding of the large-scale crustal deformation resulting from earthquakes. Using Türkiye's extensive and continuous global navigation satellite system (GNSS) network during the moment magnitude 7.8 and 7.6 Kahramanmaraş earthquakes on 6 February 2023, we show that large earthquakes can induce far-field crustal deformations (>700 kilometers), exceeding current predictions from elastic dislocation models. They can lead to the mobilization of tectonic plates and the triggering of far-field earthquakes, which carries profound implications for seismic hazard assessments and necessitates a new perspective on crustal deformation and earthquake mechanics.

Seismic slip channeling along the East Anatolian Fault illuminates long-term supercycle behavior

The two Mw > 7.5 earthquakes that struck the East Anatolian Fault (EAF), Türkiye, in 2023 caused more slip than expected, indicating that they were potentially part of a supercycle, in which the occurrence probability of a large earthquake is determined by accumulated strain rather than time since the last large earthquake. Here, we show two potential supercycles along the EAF, analyzing earthquakes from the last two millennia. Within each supercycle, seismic ruptures originated in the northeast and progressively spread southwestward with an increasing number of earthquakes until a new supercycle began with another large earthquake in the northeast. To understand the supercycle behavior, we analyze the aftershock sequences of the four most recent Mw≥6.1 mainshocks (2010-2023). This series of earthquakes progressed southwestward, characterized by an increasing diversity of focal mechanisms and a heightened dispersion of epicenters across a branched seismotectonic environment. Earthquakes in the northeast exhibit spatial and kinematic channeling along the master fault surface, effectively transferring slip southwestward and there potentially triggering dispersed and heterogeneous earthquakes. This spatiotemporal pattern seems connected with varying levels of a presumably-innate property of fault sections or regions, ruling the process of seismic slip channeling, which could also explain the behavior of long-term supercycles.

Super-shear ruptures steered by pre-stress heterogeneities during the 2023 Kahramanmaraş earthquake doublet

The 2023 M7.8 and M7.5 earthquake doublet near Kahramanmaraş, Turkey, provides insight regarding how large earthquakes rupture complex faults. Here we determine the faults geometry using surface ruptures and Synthetic Aperture Radar measurements, and the rupture kinematics from the joint inversion of high-rate Global Navigation Satellite System (GNSS), strong-motion waveforms, and GNSS static displacement. The M7.8 event initiated on a splay fault and subsequently propagated along the main East Anatolian Fault with an average rupture velocity between 3.0 and 4.0 km/s. In contrast, the M7.5 event demonstrated a bilateral supershear rupture of about 5.0-6.0 km/s over an 80 km length. Despite varying strike and dip angles, the sub-faults involved in the mainshock are nearly optimally oriented relative to the local stress tensor. The second event ruptured a fault misaligned with respect to the regional stress, also hinting at the effect of local stress heterogeneity in addition to a possible free surface effect.

Resilience and challenges of peritoneal dialysis survivors in the aftermath of the 2023 Kahramanmaraş earthquake

INTRODUCTION

Peritoneal dialysis (PD) remains understudied in disaster nephrology. This retrospective multicenter study explores the experiences of PD survivors following the February 6, 2023, Kahramanmaraş Earthquake.

METHODS

Adult PD patients from 11 affected cities were analyzed to assess challenges faced during and postearthquake, alongside clinical outcomes.

RESULTS

Among 101 participants (median age: 45 years, median PD duration: 24 months), 57 were female, with 79 on continuous ambulatory PD. Challenges included power outages and water shortages, with primary shelter in kin's houses (33%) and homes (28%). Twelve patients experienced PD program delays, and three lacked assistance postdisaster. Sixteen patients changed PD modalities, with seven experiencing postearthquake peritonitis. Clinical parameters remained stable, except for a slight decrease in hemoglobin levels.

CONCLUSION

Despite challenges, PD survivors exhibited resilience, highlighting the importance of addressing peritonitis and unusual pathogens in disaster preparedness initiatives.

Fault size-dependent fracture energy explains multiscale seismicity and cascading earthquakes

Earthquakes vary in size over many orders of magnitude, often rupturing in complex multifault and multievent sequences. Despite the large number of observed earthquakes, the scaling of the earthquake energy budget remains enigmatic. We propose that fundamentally different fracture processes govern small and large earthquakes. We combined seismological observations with physics-based earthquake models, finding that both dynamic weakening and restrengthening effects are non-negligible in the energy budget of small earthquakes. We established a linear scaling relationship between fracture energy and fault size and a break in scaling with slip. We applied this scaling using supercomputing and unveiled large dynamic rupture earthquake cascades involving >700 multiscale fractures within a fault damage zone. We provide a simple explanation for seismicity across all scales with implications for comprehending earthquake genesis and multifault rupture cascades.

Immature characteristics of the East Anatolian Fault Zone from SAR, GNSS and strong motion data of the 2023 Türkiye-Syria earthquake doublet

On February 6, 2023, an Mw 7.9 earthquake occurred in the western section of the East Anatolia Fault Zone (EAFZ). It was subsequently followed by an Mw 7.7 earthquake on the northern branch of the EAFZ, known as the Sürgü Fault Zone. Coseismic deformation fields were derived for these earthquakes using joint evaluation of near-field strong motion data, Global Navigation Satellite System data, and Synthetic Aperture Radar datasets. The coseismic slip distribution model was determined through the joint kinematic finite fault inversion. The Mw 7.9 earthquake was a left-lateral strike-slip event, predominantly occurring at depths up to 20 km. The earthquake displayed three distinct asperities that correlate well with bends and stepovers along the EAFZ. The Mw 7.7 earthquake also exhibited left-lateral strike-slip characteristics, with a major asperity along the Çardak Fault featuring a maximum slip of approximately 9.5 m at depths between 0 and 24 km. The occurrence of this unanticipated large Mw 7.9 catastrophic seismic event on a fault with low-intermediate structural maturity is noteworthy. In the vicinity of immature faults with multiple jogs, stress tends to accumulate at barrier locations. When the accumulated stress near several adjacent barriers reaches a certain threshold, it may result in the transformation of multiple barriers into asperities, triggering cascading ruptures.

High-resolution co-seismic fault offsets of the 2023 Türkiye earthquake ruptures using satellite imagery

On February 6, 2023, southern Türkiye was struck by two large earthquakes at 01:17 UTC (Mw=7.8, Pazarcık, Kahramanmaraş) and 10:30 UTC (Mw = 7.6, Elbistan, Kahramanmaraş), causing severe damage at the complex junction of the Dead Sea Fault (DSF), the Cyprus Arc and the East Anatolian Fault Zone (EAFZ). The ruptures propagated along several known strands of the southwestern termination of the EAFZ, the main Pazarcık and Karasu valley faults, and the Çardak-Sürgü fault. Here we present the high-resolution mapping of the entire coseismic surface rupture and an estimate of the rupture width, total and on-fault offset, and diffuse deformation obtained a few days to three months after the two mainshocks. The mapping is derived from image correlation of Sentinel-2 optical satellite imagery and validated with offset measurements collected on the ground. We find that the ruptures extend over lengths of 310 km and 140 km for the Mw 7.8 and Mw 7.6 mainshocks, respectively. The maximum offsets reach 7.5 ± 0.8 m and 8.7 ± 0.8 m near the epicenters of the Mw 7.8 and Mw 7.6 events, respectively. We propose a segmentation of the two ruptures based on these observations, and further discuss the location of the potential supershear rupture. The use of optical image correlation, complemented by field investigations along earthquake faults, provides new insights into seismic hazard assessment.

Resolving the slip-rate inconsistency of the northern Dead Sea fault

Reported fault slip rates, a key quantity for earthquake hazard and risk analyses, have been inconsistent for the northern Dead Sea fault (DSF). Studies of offset geological and archeological structures suggest a slip rate of 4 to 6 millimeters per year, consistent with the southern DSF, whereas geodetic slip-rate estimates are only 2 to 3 millimeters per year. To resolve this inconsistency and overcome limited access to the northern DSF in Syria, we here use burst-overlap interferometric time-series analysis of satellite radar images to provide an independent slip-rate estimate of ~2.8 millimeters per year. We also show that the high geologic slip rate could, by chance, be inflated by earthquake clustering and suggest that the slip-rate decrease from the southern to northern DSF can be explained by splay faults and diffuse offshore deformation. These results suggest a microplate west of the northern DSF and a lower earthquake hazard for that part of the fault.

Quasi-coseismic variations and geosphere coupling associated with the strong 2023 Turkey earthquakes

On 6 February 2023, two massive shallow earthquakes of Mw 7.8 and Mw 7.5 occurred successively in Turkey. Unlike earlier studies on pre-seismic anomalous signals, here we focus on the co-seismic changes in ocean, land, and atmospheric parameters associated with these two earthquakes. The quasi-coseismic variations have been clearly observed in ocean, atmosphere, and snow parameters from satellite and reanalysis datasets. Our results show a decline in the seawater temperature and salinity, and enhancement in the chlorophyll-a concentration in the eastern Mediterranean Sea associated with the earthquakes. Over the epicentral region, the total ozone column and snowfall have been observed to increase with the occurrence of earthquakes. After a detailed analysis of the hourly parameters (atmospheric pressure, air temperature, relative humidity, and wind speed), we found the atmospheric pressure variation caused by the ground motion of seismic waves is the possible reason for the co-seismic changes. Based on the results discussed in this paper, a model of multi-geosphere co-seismic response associated with the 2023 Turkey events is proposed. Additionally, our results show that the crustal motion in the high mountain region within the earthquake preparation zone could be more sensitive prior to the earthquake due to the enhancement of electric field as suggested by the theory of positive holes.

Complex multi-fault rupture and triggering during the 2023 earthquake doublet in southeastern Türkiye

Two major earthquakes (MW 7.8 and MW 7.7) ruptured left-lateral strike-slip faults of the East Anatolian Fault Zone (EAFZ) on February 6, 2023, causing >59,000 fatalities and ~$119B in damage in southeastern Türkiye and northwestern Syria. Here we derived kinematic rupture models for the two events by inverting extensive seismic and geodetic observations using complex 5-6 segment fault models constrained by satellite observations and relocated aftershocks. The larger event nucleated on a splay fault, and then propagated bilaterally ~350 km along the main EAFZ strand. The rupture speed varied from 2.5-4.5 km/s, and peak slip was ~8.1 m. 9-h later, the second event ruptured ~160 km along the curved northern EAFZ strand, with early bilateral supershear rupture velocity (>4 km/s) followed by a slower rupture speed (~3 km/s). Coulomb Failure stress increase imparted by the first event indicates plausible triggering of the doublet aftershock, along with loading of neighboring faults.