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On November 23, 2022 an Mw6.0 earthquake struck northwest Turkey. The location of this earthquake is along the boundary of the northeast striking Karadere and east striking Düzce segments of the North Anatolian Fault. Remarkably the area had already ruptured twice during the 1999 Mw7.4 Izmit and Mw7.1 Düzce earthquakes. In this study we analyzed the seismicity, aftershocks and the co-seismic rupture of the 2022 earthquake. Relocated aftershocks reveal a north dipping rupture plane consistent with the previously known fault segments. We modeled the co-seismic slip using InSAR data from Sentinel-1 satellite and near-source seismic waveforms. The kinematic model shows an up-dip bilateral rupture with majority of the slip to the west of the hypocenter. While the slip is primarily right-lateral there is significant normal component. The fact that the rupture occurred at the junction of two segments, its depth extent and oblique rake angle implies that the 2012 earthquake ruptured along a geometrical complexity that sustained a remanent slip deficit after the 1999 earthquakes.

SUMMARYThe unbroken section of the North Anatolian Fault beneath the Sea of Marmara is a major source of seismic hazard for the city of İstanbul. The northern and currently the most active branch, the Main Marmara Fault (MMF), is segmented within a shear zone and exhibits both partially creeping and locked behaviour along its 150 km length. In 2019 September, a seismic activity initiated near MMF, off-coast the town of Silivri, generating 14 earthquakes ≥ Mw 3.5 in a week. The Mw 5.8 Silivri earthquake, is the largest in the Marmara Sea since the 1963 Mw 6.3 Çınarcık earthquake. Our analyses reveal that the activity started in a narrow zone (∼100 m) and spread to ∼7 km following an Mw 4.7 foreshock within ∼2 d. The distribution of relocated aftershocks and the focal mechanisms computed from regional waveforms reveal that the Mw 5.8 earthquake did not occur on the MMF, but it ruptured ∼60° north-dipping oblique strike-slip fault with significant thrust component located on the north of the MMF. Finite-fault slip model of the main shock shows 8 km long rupture with directivity toward east, where the ruptured fault merges to the MMF. The narrow depth range of the slip distribution (10–13 km) and the aftershock zone imply that the causative fault is below the deep sedimentary cover of the Marmara Basin. The distribution of aftershocks of the Mw 5.8 event is consistent with Coulomb stress increase. The stress changes along MMF include zones of both stress decrease due to clamping and right-lateral slip, and stress increase due to loading.

Author(s): Konca, A Ozgun; Guvercin, Sezim Ezgi; Ozarpaci, Seda; Ozdemir, Alpay; Funning, Gareth J; Dogan, Ugur; Ergintav, Semih; Floyd, Michael; Karabulut, Hayrullah; Reilinger, Robert | Abstract: SUMMARY The 2017 July 20, Mw6.6 Bodrum–Kos earthquake occurred in the Gulf of Gokova in the SE Aegean, a region characterized by N–S extension in the backarc of the easternmost Hellenic Trench. The dip direction of the fault that ruptured during the earthquake has been a matter of controversy where both north- and south-dipping fault planes were used to model the coseismic slip in previous studies. Here, we use seismic (seismicity, main shock modelling, aftershock relocations and aftershock mechanisms using regional body and surface waves), geodetic (GPS, InSAR) and structural observations to estimate the location, and the dip direction of the fault that ruptured during the 2017 earthquake, and the relationship of this event to regional tectonics. We consider both dip directions and systematically search for the best-fitting locations for the north- and south-dipping fault planes. Comparing the best-fitting planes for both dip directions in terms of their misfit to the geodetic data, proximity to the hypocenter location and Coulomb stress changes at the aftershock locations, we conclude that the 2017 earthquake ruptured a north-dipping fault. We find that the earthquake occurred on a 20–25 km long, ∼E–W striking, 40° north-dipping, pure normal fault with slip primarily confined between 3 and 15 km depth, and the largest slip exceeding 2 m between depths of 4 and 10 km. The coseismic fault, not mapped previously, projects to the surface within the western Gulf, and partly serves both to widen the Gulf and separate Kos Island from the Bodrum Peninsula of SW Anatolia. The coseismic fault may be an extension of a mapped, north-dipping normal fault along the south side of the Gulf of Gokova. While all of the larger aftershocks are consistent with N–S extension, their spatially dispersed pattern attests to the high degree of crustal fracturing within the basin, due to rapid trenchward extension and anticlockwise rotation within the southeastern Aegean.

On 2020 October 30, an Mw6.9 earthquake struck offshore Samos Island. Severe structural damages were observed in Greek Islands and city of Izmir (Turkey). 114 people lost their lives and more than a thousand people were injured in Turkey. The earthquake triggered local tsunami. Significant seismic activity occurred in this region following the earthquake and ~1800 aftershocks (M>1) were recorded by KOERI within the first three days. In this study, we analyze the slip distribution and aftershocks of the 2020 earthquake.For the aftershock relocations, the continuous waveforms were collected from NOA, Disaster and Emergency Management Authority of Turkey (AFAD) and KOERI networks. The database was created based on merged catalogs from AFAD and KOERI. For estimating optimized aftershock location distribution, the P and S phases of the aftershocks are picked manually and relocated with double difference algorithm. In addition, source mechanisms of aftershocks M>4 are obtained from regional body and surface waveforms.The surface deformation of the earthquake was obtained from both descending and ascending orbits of the Sentinel-1 A/B and ALOS2 satellites. Since the rupture zone is beneath the Gulf of Kusadası, earthquake related deformation in the interferograms can only be observed on the northern part of the Samos Island. We processed all possible pairs chose the image pairs with the lowest noise level.In this study, we used 25 continuous GPS stations which are compiled from TUSAGA-Aktif in Turkey and NOANET in Greece. In addition to continuous GPS data, on 2020 November 1, GPS survey was initiated and the earthquake deformation was measured on 10 GNSS campaign sites (TUTGA), along onshore of Turkey.The aim of this study is to estimate the spatial and temporal rupture evolution of the earthquake from geodetic data jointly with near field displacement waveforms. To do so, we use the Bayesian Earthquake Analysis Tool (BEAT).As a first step of the study, rectangular source parameters were estimated by using GPS data. In order to estimate the slip distribution, we used both ascending and descending tracks of Sentinel-1 data, ALOS2 and GPS displacements. In our preliminary geodetic data based finite fault model, we used the results of focal mechanism and GPS data inversion solutions for the initial fault plane parameters. The slip distribution results indicate that earthquake rupture is ~35 km long and the maximum slip is ~2 m normal slip along a north dipping fault plane. This EW trending, ~45° north dipping normal faulting system consistent with this tectonic regime in the region. This seismically active area is part of a N-S extensional regime and controlled primarily by normal fault systems.AcknowledgementsThis work is supported by the Turkish Directorate of Strategy and Budget under the TAM Project number 2007K12-873.

Based on >20 years of GPS observations and seismological works, direct constraints on the strain accumulation along the Main Marmara Fault (MMF) show different characteristics from Princess Islands to Ganos Fault. Ganos and Princess Island segments identified as locked based on GPS and seismological observations while the part of the Central Marmara segment show partially creeping behaviour. Moreover, around the Kumburgaz Basin, GPS data could be explained by creep models in contrast to fully locked seismic models. Clearly, there are many puzzling questions on the nature of strain accumulation on the MMF, under the constrain of various data sets. In order to contribute to a better understanding of this fault the observation capacity of geodesic network has been increased along the northern coast of the Marmara Sea and supported by seismological stations as well as Marine Geodesy.In September, 2019, an intense earthquake activity started between Central Marmara and Kumburgaz Basin. The mainshock occurred on 26 September 2019 (Mw5.8) as a largest earthquake, since 1963 Mw6.3 Cinarcik earthquake, in the Marmara Sea. A foreshock activity started 4 days before the mainshock and the largest one (Mw4.7) observed on September 24, close to the mainshock. The mechanisms of the mainshock and the large aftershocks as well as foreshocks are dominantly strike-slip with a significant reverse component. The aftershocks are located on the north of the MMF trace.Here we investigate the geodetic data related to this event, with the aim to shed some light on the complexly segmented MMF. We observed co-seismic offsets at the nearest 6 GPS stations (~12-20 km far to the epicenter) along the northern coastline of the Sea of Marmara. The estimated offsets are not big and change between 1-3 mm on horizontal and 1-10 mm on vertical components. All of the stations are located on the northern part of the hypocenter and exhibit predominant NS-direction movement, which is inconsistent with a primarily E-W right lateral transform system. Instead, the co-seismic pattern can be explained with a complex earthquake mechanism which has a dominant reverse component while the strike-slip component is relatively insignificant, based on Okada-type elastic models and geodetic moment magnitude obtained as ~6.2. The total cumulative moment using geodesy is much higher than the total seismic cumulative moment of earthquake activity (~M5.9), and the thrust component is also more dominant in comparison the focal mechanisms from regional data. Obviously, geodetic co-seismic offsets estimated from daily-based data and they include pre-and post-earthquake deformations. In addition, the tide-gauge data (station distance is 25 km far to epicenter) was analyzed and it shows the strong variations after Mw 4.7 and they faded out after Mw5.8. This sea level change, which temporally correlates with the seismic activity, gives important evidence about the possibilities of pre-earthquake activity. Using GPS time series, we intend to explore the pre-earthquake anomalies and, to reduce the discrepancy between seismological and geodetic models. (This study is supported by TUBITAK 1001 Project no: 117Y278).

Southwestern Anatolia is part of a N-S extensional regime mainly driven by rollback along the Hellenic subduction zone beneath the Aegean Sea. This seismically active area is controlled primarily by normal fault systems. The fault structures in the region are segmented and in many cases seismic interaction between these segments can be observed.2017 seismic activity along the Eastern and Western edges of Gökova Bay. Within the same year, three separate moderate sized (Mw~5) events took place near the town of Ula (Muğla) on the eastern edge of Gökova Bay. One of these earthquakes occurred in April before the Bodrum-Kos earthquake while the other pair occurred in November within two days.We relocated all the events that occurred in Ula region in 2017 and remodeled the source mechanisms from regional seismic waveforms by using Bayesian Earthquake Analysis Tool (BEAT). The surface deformations can also be clearly observed from InSAR tracks of both ascending and descending orbits. Because of the large noise margins of the interferograms, atmospheric noise corrections and high resolution DEM data were used.Due to temporal and spatial proximity of the two Mw~5 events during the November sequence, InSAR yields only cumulative deformation of the earthquakes. Therefore, we determined the contribution of each event to the cumulative static displacements observed by InSAR data, using the source models from seismic waveforms. The locations and the source mechanisms of the two Mw~5 earthquake are consistent and explain the observed surface deformation.Our results imply that these earthquakes occurred on a previously unknown normal fault rather than the southeastern branches of the nearby Muğla Fault as proposed earlier. The results are consistent with the recently mapped fault structure by Akyüz et al. (2018). The November activity implies EW trending, south dipping normal faulting system and the change in the strike direction of the fault on the eastern edge can be clearly seen both InSAR and waveform modelling results of April activity.Co-seismic and post-seismic InSAR analysis shows that the seismic activity following the 2017 Mw6.6 Bodrum-Kos propagated from western Gökova Bay where rupture occurred toward east including the Ula region. A long term comparison of seismicity beneath Gökova Bay and Ula region shows that the seismicity in these two regions are temporally correlated. Hence, while the aforementioned moderate sized earthquakes are not directly triggered by the Bodrum-Kos earthquake, increased seismic activity following Bodrum-Kos earthquake shows that the stress changes in these two regions affect each other. The location errors of the events especially the depth errors in the catalogs and the active fault structure in the area cannot be realized without any geodetic or seismic data analysis. This study claims that the interpretations of the moderate size earthquakes should be studied by using multidisciplinary data sets.ACKNOWLEDGEMENTSThis work is supported by the Turkish Directorate of Strategy and Budget under the TAM Project number DPT2007K120610.

The North Anatolian Fault (NAF) is a 1600 km dextral transform fault accommodating the motion between Anatolia and Eurasia Plates. The segments beneath the Marmara Sea, are the only part of the NAF that did not break since the 20thcentury. Recent studies show that this 150 km seismic gap is characterized by heterogeneous interseismic behavior and significantly high background seismicity with respect to the other parts of the NAF.On September 24 2019, an activity started north of the Main Marmara Fault (MMF) including a Mw4.7 earthquake, which led to the Mw5.8 mainshock several days later. The 2019 Mw5.8 Silivri earthquake is the largest since 1963 Mw6.3 Cinarcik earthquake in the Marmara Sea. This sequence occurred at a location that is immediate north west of the Central Basin; between a zone that is possibly partially creeping (Central Basin) to the west and a possibly locked segment to the east (Kumburgaz Basin). In this study we used template search for detection of earthquakes, relocated the earthquakes, obtained focal mechanism solutions of earthquakes that are M>4 and obtained a finite-fault slip model of the Mw5.8 mainshock. Using template cross-correlation, a total of 400 earthquakes were detected in this sequence. The activity started in a relatively narrow zone and spread to larger distances following the Mw4.7 mainshock. The depth distribution shows that the earthquakes are confined to a narrow zone between the depths of 9-13 km. The focal mechanisms show that there are two clusters; the cluster to the northwest show a ~70°north dipping fault with rake angles about ~160°, while the activity toward east converges to the Main Marmara Fault and dip angle is close to ~70°with rake angles of ~140°. The finite-fault model shows a bilateral rupture that propagated down-dip from the hypocenter.We conclude that the seismic activity occurred on a fault that is within the Main Marmara Shear Zone beneath the sedimentary basin. This secondary fault possibly connects to the Main Marmara Fault to the east. There is no evidence that the causative fault continues up-dip into the basin. Another characteristic of this sequence is that all of the focal mechanisms show significant thrust component in addition to the expected right-lateral motion. The January 2020 Mw4.7 earthquake that occurred in the same zone between the two clusters have predominantly thrust mechanism, confirming that this zone is under local compression. The observed thrust component is possibly related to change of the width of the shear zone with narrowing from Central Basin to the west to Central High to the east and/or the change of the interseismic behavior of the fault from partially creeping Central Basin and locked Kumburgaz Basin segments.

We studied the mechanisms and spatiotemporal distribution of aftershocks of the Mw 7.1 Van earthquake, in Eastern Turkey. The Van earthquake occurred on an E-W trending thrust fault, in a region under N-S compression due to the convergence of the Arabian plate toward Eurasia. We relocated the seismicity by combining catalogs from two agencies and studied the source mechanisms of the Mw 3.5–5.6 aftershocks using regional body and surface waves. In addition to the aftershocks with thrust mechanism on the mainshock fault, we identified three clusters with strike-slip activity. Two of the clusters are on the left-lateral faults perpendicular to the mainshock fault and are located at the lateral termination of the co-seismic rupture in each direction. Both western and eastern strike-slip clusters were triggered within the first few hours following the mainshock. They were initiated very close to the mainshock rupture plane and propagated away toward the south and north respectively. These two dominantly strike-slip zones are connected to the mainshock fault at a depth of 15 km and possibly determined the lateral extent of the 2011 rupture. This system of two bounding left lateral faults with a thrust fault in between is overall consistent with the N-S convergent tectonic regime in the region. The complex geometry explains unexpected post-seismic motion at a GPS site and can be used to improve the post-seismic slip estimate of the earthquake. The third strike-slip cluster with 17 days delay occurred on an E-W trending right-lateral fault and 40 km on the south of the mainshock. The three activated faults have experienced Coulomb stress increase due to co-seismic rupture. In addition, most of the seismicity has occurred in regions that experienced Coulomb stress increase.

In the Eastern Mediterranean, the convergence of Nubia and Eurasia is accommodated along the Hellenic and Cyprus Trenches. The plate geometry and mode of convergence to the east of the Hellenic Trench remains poorly understood. Specifically, along the west of Cyprus, tomography models reveal NW striking high velocity anomaly, which is interpreted as a slab named as the Antalya slab. However, near surface observations pertaining to the top 15 km of the convergence zone show no evidence of an active subduction in the region. In this study, we investigate the seismic activity along the Antalya slab in order to constrain the mode of convergence and the geometry along this plate boundary. Towards this end, we obtain a new focal mechanism catalogue with reliable centroid depths for earthquakes Mw > 4 from regional waveforms by using path dependent seismic velocity models. Our results indicate that the subduction is still active along the plate boundary segment between Cyprus and Anaximander seamount. The earthquakes along the slab interface reveal a NE-dipping slab with a dip angle of ~35°. Slip vectors show a pure convergent motion which is consistent with relative motion of Anatolia with respect to Nubia. We also identify a number of intraslab earthquakes down to a depth of 120 km along the Antalya slab. The T-axis of intraslab earthquakes show down-dip extension consistent with negatively buoyant subducting slab. The Paphos fault bounds the Antalya slab to the east where previously large right-lateral earthquakes occurred, which marks the relative motion of the Antalya slab with respect to the eastern Cyprus slab. Based on slab isodepth contours of the slab interface, we calculate ~100 km offset between the 80 km depth contours of the Antalya and Cyprus slabs. The western boundary of the Antalya slab possibly lies between the Anaximander and Anaximenes seamounts, where several left-lateral earthquakes are obtained. The western boundary of the Antalya slab can also be identified from orientation change of normal fault earthquakes along overriding plate which shows the limit of N-S extension due to roll-back of the neighboring Hellenic slab.

In this article, we consider the problem of finding the effective moment tensor for shear slip along a bimaterial interface. When the slip occurs at the jump of the values of elastic parameters, it is not clear how the elasticity tensor of each side should be combined in a unique way to obtain the effective elasticity tensor that then can be used in the moment tensor expression. Moreover, the Green’s function of the medium is not differentiable at the bimaterial interface, which prevents writing down the moment tensor form of the representation theorem, therefore leading to an ambiguity. In this article, we first show that the derivative of the Green’s function can be obtained once the Green’s function is considered as a hyperfunction, which is an equivalent concept to generalized functions or distributions. The resulting Green’s function at the bimaterial interface is the average of the Green’s function derivatives evaluated on either side. Finally, to obtain the effective elastic parameters, we used the equivalence of the unambiguous potency form and the moment tensor form of the representation theorems constrained with the boundary conditions, which are the continuity of the traction acting on the fault and the tangential strain across the fault. A unique solution is obtained for the isotropic case as well as transversely isotropic and orthotropic media if the symmetry axes of the tensors are aligned with the fault orientation. However, for general anisotropy or arbitrarily oriented structures, the solution is nonunique, for which certain physical constraints such as positive definiteness of the elasticity tensor can be used to confine the solution.

We inferred the rupture process of the 2015 Lefkada earthquake by combining teleseismic and near-field strong motion data, together with static and dynamic GPS displacements. The joint inversion of all data sets revealed a relatively complex slip pattern with a heterogeneous distribution. Slip is confined in the upper 10 km. Two principal asperities with peak slip amplitude of 2.35 m, which released 65% of the total seismic moment, were recovered southwest of the epicenter. Remarkably, the 2015 earthquake ruptured the part of the Cephalonia Transform Fault Zone that remained unbroken during the 2003 event, revealing a pattern of rupture segmentation along the fault zone. In this context the Lefkada segment can be divided into a northern and southern part. Preseismic deformation onshore southern Lefkada revealed that since the 2003 rupture, the northern part of the Lefkada segment continuously loaded the southern part, which eventually broke during the 2015 event.

SUMMARY Slip-rate function and the rupture velocity are two important parameters that are critical in understanding the physics of earthquakes. When conventional objective functions are used, the slip-rate function is not well resolved from seismic data. Here, we propose a new method to obtain the slip-rate function by utilizing the near-field phases recorded near the fault rupture. First we illustrate the sensitivity of near-field phases to the moment accumulation and modify the objective function in order to take advantage of this sensitivity. By utilizing near-field P waves along with S pulses on the near-source records and using a Bayesian approach, we show that we can constrain the average slip-rate function as well as the average rupture velocity for a strike-slip earthquake. As a case example, we apply this technique to the record of the 2003, Mw6.6 Bam Earthquake. Our results indicate an asymmetric slip-rate function, with acceleration duration of about 0.4s, and deceleration duration of 1.4s. The slip-rate function obtained from kinematic modelling of the 2003 Bam earthquake is consistent with those predicted by dynamic rupture simulations. The rupture velocity is about 82–90 per cent of the shear wave velocity, implying a sub-Rayleigh rupture velocity close to the Rayleigh wave speed. In future cases where abundant near-source strong-motion data exist and slip is well constrained, the method described in this study can be applied to obtain the variation of the slip-rate function along the fault which would improve our understanding of earthquake rupture physics.

We analyze the rupture process of the 1999 M_w 7.1 Duzce earthquake using seismological, remote sensing, and geodetic data. Ground deformation measured from the subpixel cross correlation of Satellite Pour l'Observation de la Terre (SPOT) images reveals a 55 km long fault trace and smooth surface-slip distribution peaking at 3.5–4 m. The westernmost segment overlaps for over 10 km with ruptures from the M_w 7.4 Izmit earthquake. The 15 km long easternmost segment, which cuts across mountainous topography, had not been reported previously. We determine a well-constrained source model using a four-segment fault geometry using constraints on surface fault slip and inverting Global Positioning System and Interferometric Synthetic Aperture Radar data along with strong-motion records. Our results show that some variability of the rupture velocity and an eastward supershear velocity are required to fit the strong-motion data. The rise time, up to 6 sec, correlates with cumulative slip, suggesting a sliding velocity of about 1 m/sec. The source model predicts teleseismic waveforms well, although early by 2 sec. This time shift is probably due to the weak beginning of the earthquake that is not observable at teleseismic distances. Strong-motion records are relatively well predicted from a source model derived from the teleseismic data using the fault geometry derived from the satellite images. This study demonstrates the benefit of using accurate fault geometries to determine finite-fault source models.

We analyze the M_w 7.6 Kashmir earthquake of October 8, 2005, using sub-pixel correlation of ASTER images to measure ground deformation, and modeling seismic waveforms. The surface rupture is continuous over a distance of 75 km and cuts across the Hazara syntaxis reactivating the Tanda and the Muzaffarabad faults. North of Muzaffarabad the surface rupture coincides approximately with the MBT, on the southwestern flank of the syntaxis, although the two faults have opposite dip angles. The rupture terminates abruptly at the hairpin turn of the MBT showing a strong structural control. The fault offset is 4 m on average and peaks to 7 m northwest of Muzaffarabad. The rupture lasted about 25 s and propagated updip and bi-laterally ~2 km/s, with a rise time of 2–5 s. The shallowness and compactness of the rupture, both in time and space, provide an explanation for the intensity of destructions. This kind of analysis could be achieved as soon as a post-earthquake image is available, and would provide key information for early assessment of damages. The study sheds some light on seismic hazard in the Himalaya, and raises concern regarding the possibility of a repetition of the 1555 event which presumably ruptured the Himalayan front south of the Kashmir basin and may have reached a magnitude M_w > 8.

The great Sumatra - Andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones(1-4). In March 2005, the Sunda megathrust ruptured again, producing an event(5) of moment magnitude (M-w) 8.6 south of the 2004 rupture area, which was the site of a similar event in 1861 (ref. 6). Concern was then focused on the Mentawai area, where large earthquakes had occurred in 1797 ( M-w = 8.8) and 1833 (M-w = 9.0)(6,7). Two earthquakes, one of M-w = 8.4 and, twelve hours later, one of M-w = 7.9, indeed occurred there on 12 September 2007. Here we show that these earthquakes ruptured only a fraction of the area ruptured in 1833 and consist of distinct asperities within a patch of the megathrust that had remained locked in the interseismic period. This indicates that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture. This variability probably arises from the influence of non- permanent barriers, zones with locally lower pre- stress due to the past earthquakes. The stress state of the portion of the Sunda megathrust that had ruptured in 1833 and 1797 was probably not adequate for the development of a single large rupture in 2007. Themoment released in 2007 amounts to only a fraction both of that released in 1833 and of the deficit of moment that had accumulated as a result of interseismic strain since 1833. The potential for a large megathrust event in the Mentawai area thus remains large.

The 2005 Mw 8.6 Nias–Simeulue earthquake was caused by rupture of a portion of the Sunda megathrust offshore northern Sumatra. This event occurred within an array of continuous Global Positioning System (gps) stations and produced measurable vertical displacement of the fringing coral reefs above the fault rupture. Thus, this earthquake provides a unique opportunity to assess the source characteristics of a megathrust event from the joint analysis of seismic data and near-field static co-seismic displacements. Based on the excitation of the normal mode data and geodetic data we put relatively tight constraints on the seismic moment and the fault dip, where the dip is determined to be 8° to 10° with corresponding moments of 1.24 × 1022 to 1.00 × 1022 N m, respectively. The geodetic constraints on slip distribution help to eliminate the trade-off between rupture velocity and slip kinematics. Source models obtained from the inversion of various combinations of the teleseismic body waves and geodetic data are evaluated by comparing predicted and observed long-period seismic waveforms (100–500 sec). Our results indicate a relatively slow average rupture velocity of 1.5 to 2.5 km/sec and long average rise time of up to 20 sec. The earthquake nucleated between two separate slip patches, one beneath Nias and the other beneath Simeulue Island. The gap between the two patches and the hypocentral location appears to be coincident with a local geological disruption of the forearc. Coseismic slip clearly tapers to zero before it reaches the trench probably because the rupture propagation was inhibited when it reached the accretionary prism. Using the models from joint inversions, we estimate the peak ground velocity on Nias Island to be about 30 cm/sec, an order of magnitude slower than for thrust events in continental areas. This study emphasizes the importance of utilizing multiple datasets in imaging seismic ruptures.

A novel model was used to analyze the experimental threshold and efficiency data of continuous-wave Cr4+:forsterite lasers operated around room temperature by taking into account the temperature dependence of the fluorescence lifetime, pump absorption saturation, and excited-state absorption at the lasing wavelength. The best-fit values of the stimulated emission cross-section and the excited-state absorption cross-section were determined to be 1.23x10^-19 cm2 and 0.26x10^-19 cm2, respectively. The numerical calculations further predict the optimum crystal length and absorption coefficient to be 2 cm and 0.34 cm-1 for room-temperature Cr4+:forsterite lasers.

Experimental and numerical methods were employed to investigate the influence of thermal effects in room-temperature continuous-wave Cr4+:YAG lasers. Pump saturation, laser threshold, and laser efficiency data were first analyzed by accounting for the temperature dependence of the fluorescence lifetime, pump-induced heating in the gain medium, excited-state absorption at the lasing wavelength, and saturation effects. Best-fit values of the absorption, emission, and excited-state absorption cross sections were determined to be 11.2×10−19 cm2, 0.47×10−19 cm2, and 0.093×10−19 cm2, respectively. Based on the best-fit cross-section values, numerical calculations show that the optimum crystal length and absorption coefficient are 2 cm and 0.56 cm−1, respectively.

Continuous-wave power performance of a Cr2+:znSe laser was investigated at 2.474 ?m. End pumped by a 1.583-?m NaCl:OH- laser, the resonator with a 3% transmitting output coupler produced as high as 250 mW of output power with a slope efficiency of 24.2%. Analysis of the laser efficiency data shows that the magnitude of the excited-state absorption cross section is less than 5% of the emission cross section in agreement with spectroscopic results. Numerical calculations further predict the optimum crystal length and absorption coefficient to be 2.5 cm and 0.49 cm-1, respectively, for continuous-wave operation., National Science Foundation; Scientific and Technological Research Council of Turkey (TÜBİTAK)