Papers by Pinar Buyukakpinar
On 23 April 2025, a Mw 6.3 earthquake struck the Sea of Marmara near the Kumburgaz segment of the... more On 23 April 2025, a Mw 6.3 earthquake struck the Sea of Marmara near the Kumburgaz segment of the North Anatolian Fault (NAF), triggering over 500 aftershocks within 15 days. This study presents a rapid assessment of the event through aftershock relocation using double-difference technique, full moment tensor inversion of the mainshock, and ground motion analysis. The mainshock exhibited a strike-slip mechanism at a depth of 6 km with a significant non-double-couple component (40%). The aftershocks mostly occurred east of the mainshock, primarily within 10 km depth. Shakemaps derived from ground motion recordings highlight peak ground accelerations exceeding 210 cm/s 2 east of the mainshock in western Istanbul and Modified Mercalli Intensities reaching level 6. The ground motion prediction equation developed for the region slightly underestimated the peak ground motions in short-period pseudo-spectral acceleration (PSA) and peak ground acceleration (PGA). Comparison with Turkish seismic design codes revealed that short-period PSA reached code limits in some stations, raising concerns for structural resilience especially in older buildings in those areas.
From September 2022 to August 2023, a temporary large-N seismic experiment with more than 494 sta... more From September 2022 to August 2023, a temporary large-N seismic experiment with more than 494 station locations was conducted in the Eifel volcanic fields of southwest Germany, where massive intracontinental maars and explosive centers are distributed. The last major eruption occurred at the Laacher See volcano (LSV) only 13 ka ago. The exceptional data set was used to image V P and V P / V S ratio structures with a minimum grid spacing of 2 km. The final results were interpreted with local seismicity and other geophysical data. In addition to major tectonic features, our 3-D tomographic models resolve the LSV reservoir-structure between 2 and 10 km depth with high V P / V S ratio. The cylindrical anomaly has a volume of approximately 75 km 3 and dips 53°to the southeast, where it crosses the Siegen thrust at a depth of about 10 km. Microearthquakes cluster at the margins of the high V P / V Slow V P anomalies, indicating that the zones are under high fluid pressure or elevated temperatures. This anomaly is also located above the crust-mantle seismic channel, characterized by deep low-frequency volcanic earthquakes at depths of 10-43 km, suggesting that the anomalous zones may be related to the migration of magmatic fluids. Plain Language Summary The Eifel region of southwest Germany is a well-known volcanic field in Central Europe. A seismic network with a large number (large-N) of stations was deployed here for about 1 year to monitor the local seismicity. Our study utilized the compressional (P-wave) and shear (S-wave) waves generated by local earthquakes to image the subsurface structure with unprecedented resolution. Through traveltime tomography, we calculated the high-resolution models of P-wave velocity (V P) and P-wave to S-wave velocity ratio (V P / V S) models. These models resolve the reservoirs beneath the Laacher See volcano in the upper crust. This reservoir structure is characterized by a cylindrical anomaly extending to a depth of about 10 km with low V P and high V P / V S , and may indicate fluid-partial-melt bearing zones. At greater depths in a similar location, previous studies have also identified a channel for upward migration of magma and fluids from the mantle, indicated by deep, low-frequency volcanic earthquakes. Geochemical analysis of gases also suggests that the reservoir beneath Laacher See appears to be fed from mantle sources. Other shallower anomalies are observed around neighboring volcanoes such as Rieden and Korretsberg.
We introduce a data-driven method and software for detecting and locating earthquakes in large se... more We introduce a data-driven method and software for detecting and locating earthquakes in large seismic datasets. By combining seismic phase arrival annotations, delivered by neural network phase pickers, and waveform stacking with an adaptive octree search, we can automatically detect and locate seismic events even in noise-dominant seismic data. The resolution of the search volume is iteratively refined toward the seismic source location; this strategy facilitates an efficient, fast, and accurate search. We present a user-friendly and high-performance open-source software framework based on established frameworks, featuring event detection in layered 1D and complex 3D velocity models and event feature extraction capabilities, such as moment and local magnitude calculation from peak ground motions. We incorporated station-specific corrections and source-specific station terms into the search to enhance the location accuracy. We demonstrate and validate our approach by extracting extensive earthquake catalogs from large seismic datasets in different regions and geological settings: (1) Reykjanes Peninsula, Iceland; (2) Eifel volcanic region, Germany; and (3) Utah FORGE, USA. We capture seismic events from tectonic activity, volcanic swarms, and induced microseismic activity with magnitudes ranging from-1 to 5. Such precise and complete earthquake catalogs contribute to the interpretation and understanding of otherwise hidden subsurface processes. Non-technical summary We present a new method and open-source software for automatically detecting and localizing earthquakes and microseismicity in large seismic datasets recorded by seismometers. The technique can detect natural earthquakes, such as tectonic faulting events, volcano-tectonic swarm activity, and induced seismicity from well operation in oil and gas or geothermal exploitation. Our method uses machine learning and an adaptive focusing mechanism to efficiently search through large amounts of continuous seismic data and detect and locate earthquake events. We present an open-source software written in Python, qseek, for this purpose. To test and showcase the method, we look at seismic data from (1) Iceland, where a volcano-tectonic sequence was recorded, (2) a large dataset from the Eifel Volcanic Region, Germany, and (3) microseismicity recorded at Utah FORGE, USA, a field-scale geothermal lab. By detecting and locating the small seismicity underground, we make otherwise hidden processes within the Earth visible. Our robust and easy-to-use method contributes to understanding natural seismic activity and manmade seismicity.
The Neuwied Basin within the East Eifel Volcanic Field (EEVF) is characterized by increased micro... more The Neuwied Basin within the East Eifel Volcanic Field (EEVF) is characterized by increased microseismicity, long hypothesized to be linked to the subsurface Ochtendung Fault Zone (OFZ). However, the source of this unrest remained elusive due to limited hypocentre resolution. Here, we present an extended local earthquake catalogue, compiled from a year-long Large-N deployment and a machine learning-based detection and location approach, including over 1000 microearthquakes recorded between September 2022 and August 2023. This highresolution data set reveals new seismicity clusters, repeated waveforms and distinct temporal bursts of activity, suggesting fluid-induced earthquake triggering. Probabilistic moment tensor inversion for 192 high-quality events (M w 0.6-2.7) resolves predominantly strike-slip faulting along the OFZ, with localized clusters of normal faulting nearby, potentially associated with a previously unknown border fault of the NWB. Notably, we observe systematic rotations in P-axis orientations along the OFZ, which we interpret as localized stress perturbations induced by an overpressured reservoir beneath the Laacher See volcano-the youngest explosive eruption centre in the EEVF. These patterns, coupled with elevated magmatic CO 2 emissions in the region and high waveform similarity, suggest that active magmatic and transcrustal fluid processes are influencing the stress regimes and driving the seismicity in the NWB. Our high-resolution seismicity and moment tensor catalogue offers new insights into the interplay between tectonics and fluid-driven processes beneath the youngest volcanoes in the EEVF.
The understanding of the magma system beneath intracontinental volcanic fields depends critically... more The understanding of the magma system beneath intracontinental volcanic fields depends critically on our ability to resolve small-sized anomalies distributed over large areas of hundreds of kilometres. Magmatic reservoirs co-exist at different depths in the upper mantle and crust and may consist of extensive zones of crystal mush, swarms of sills and dikes of different ages and states, pore space saturated by volatiles or melt, or larger-volume, differentiated magma. Passive seismological experiments with a large number of sensors deployed with small interstation spacings, combining different types of sensors and fibre-optic sensor technology, have great promise for addressing the resolution to capture the distributed magmatic system. We report on a one-year, large-N experiment in the Quaternary volcanic fields of the Eifel, Germany, where more than 494 seismic stations were deployed and combined with a 64 km long DAS cable and permanent stations. A cloud-based, open-source GIS system was implemented to address logistical challenges and ensure data quality combined with seismological analysis and visualisation tools. We present initial results to test the potential of such an extensive waveform database and automated processing for locating small earthquakes and imaging crustal and upper mantle anomalies using techniques such as ambient noise cross-correlation, receiver functions, and SKS splitting.
Physics of the Earth and Planetary Interiors, 2025
Despite the occurrence of large, past earthquakes in the Central Betic Range (Southern Spain), se... more Despite the occurrence of large, past earthquakes in the Central Betic Range (Southern Spain), seismicity recorded with digital seismographs is limited to small magnitude events. Here we are interested in the three strongest events (M W 4.5 to 5.0), of which source models are unclear for different reasons: The June 20th 1979 and June 24th 1984 earthquakes are still characterized by a lack of regional recordings, while the August 12th 2021 earthquake occurred during a teleseismic M8 event. We use beamforming at distant seismic arrays and waveform modelling of depth phases to estimate source parameters for seven earthquakes altogether. The technique is successful at reproducing P-waveforms and at estimating the depth of four recent (1997-2021) earthquakes with M W > 4. In addition, it is also used along with an inverse scheme that yields source mechanisms similar to regional moment tensor solutions. Inversion suggests normal faulting at depths of 7 km and 9 km for the 1984 and 2021 events, which is consistent with our understanding of regional seismotectonics. Beamforming has been able to extract the 2021 waveforms from the M8 coda wavefield, and could be a suitable approach also for other cases of earthquake coincidence. The most noteworthy result is a strike-slip mechanism at 60 km depth for the 1979 earthquake, which is a singular subcrustal event in this area and might be related to tearing at the edge of the Gibraltar slab.
The Seismic Record, 2025
Büyükakpınar, P., Carrillo‐Ponce, A. C., Munir, M. B., Karasözen, E., Tanyas, H., Ertuncay, D., P... more Büyükakpınar, P., Carrillo‐Ponce, A. C., Munir, M. B., Karasözen, E., Tanyas, H., Ertuncay, D., Palliath, A., & Gorum, T. (2025). Seismic, field, and remote sensing analysis of the 13 February 2024 Çöpler Gold Mine landslide, Erzincan, Türkiye. The Seismic Record, 5(2), 165–174. https://doi.org/10.1785/0320250007
We analyze seismicity and centroid moment tensors (CMTs) on the Reykjanes Peninsula, Iceland, dur... more We analyze seismicity and centroid moment tensors (CMTs) on the Reykjanes Peninsula, Iceland, during the early phase of a widespread unrest period that led to multiple fissure eruptions between 2021 and 2024. We use a dense temporary seismic array, together with fiber-optic distributed acoustic sensing data, and incorporate first-motion polarities into the CMT inversion to improve accuracy, generating a total of 300 robust CMT solutions for magnitudes Mw > 2.5, focusing on 83 reliable Mw > 2.7 earthquakes for interpretation. The CMTs predominantly exhibit shallow strike-slip faulting, with a few normal faulting events compatible with tectonic stress. Interestingly, significant positive isotropic components are resolved, contributing up to 15% of the moment release. We also develop a new high-resolution seismic catalog of 34,407 events and show that larger shallow earthquakes at the plate boundary are preceded by the slow upward migration of microearthquakes from below, suggesting that intruding magmatic fluids interact with the oblique plate boundary to trigger slow slip events. We interpret our results as the seismic response to transtensional motion at the plate boundary in the brittle upper crust under shear, in response to stress changes induced by the intrusion of pressurized fluids in the lower crust. The complex interaction of multiple subparallel dikes with the plate boundary fault contributes to a broader deformation band that accommodates both tectonic and magmatic stresses. While the location and magnitude of the CMTs correlate with reactivated surface fractures and faults, the locations of intense, deep microseismic swarms indicate the sites of future fissure eruptions.
Seismica, 2023
Within two hours on 01 July 2022, three earthquakes of Mw 5.8-6.0 hit the SE Fars Arc, Iran. In t... more Within two hours on 01 July 2022, three earthquakes of Mw 5.8-6.0 hit the SE Fars Arc, Iran. In the following months, the region, characterized by the collision of the Iranian and the Arabian plate, thrust faulting, and salt diapirism, was stroke by more than 120 aftershocks of mL 3.1-5.2, of which two of the largest events occurred within one minute on 23 July 2022 in spatial vicinity to each other. We analyzed both the large mainshocks and aftershocks using different techniques, such as the inversion of seismic and satellite deformation data in a joint process, and aftershock relocation. Our results indicate the activation of thrust faults within the lower sedimentary cover of the region along with high aftershock activity at significantly larger depths, supporting the model of a crustal strain decoupling during the collision in the Fars Arc. We resolved a magnitude difference of > 0.2 magnitude units between seismic and joint seismic and satellite deformation inversions probably caused by afterslip, thereby allowing to bridge between results from international agencies and earlier studies. We also find evidence for an event doublet and triplet activating the same or adjacent faults within the sedimentary cover and the basement. Non-technical summary On 01 July 2022, three moderate earthquakes with magnitudes of 5.8-6.0 occurred in the Zagros mountain range in the Hormozghan province, SE Iran. Their close occurrence in space and time impedes the analysis of such events. Using seismic and satellite deformation data with well-proven and newly developed earthquake parameter estimation tools, we found evidence for south-dipping thrust events within the shallow sedimentary layer. The relocation of more than 120 aftershocks with local magnitudes 3.1-5.2 revealed a strong spatial concentration in larger depths of 10-15 km beneath the mainshocks. This result is consistent with the scenario of shallow-depth mainshocks followed by separated, deeper aftershock sequences, as already observed at the western edge of the Hormuz Strait.
3d Structural Modelling of Kopili Fault Zone in Ner India Utilising Small-to-Moderate Earthquakes: Seismotectonics and Kinematics Implications
Social Science Research Network, 2023
Rupture processes of the 2023 Türkiye earthquake sequence: Main- and aftershocks
On February 6, 2023, southeastern Turkey was hit by two of the most devastating earthquakes in th... more On February 6, 2023, southeastern Turkey was hit by two of the most devastating earthquakes in the instrumental period of the country, with Mw 7.7-7.8 and Mw 7.6, respectively. Both earthquakes caused massive damage and in total tens of thousands of casualties in Turkey and Syria. In this study, we analyze the rupture processes of main- and aftershocks by combining different seismic source characterization techniques using teleseismic, regional and local data. We perform finite source inversion and back projection-based analyses for the two main shocks and invert for probabilistic centroid moment tensor solutions of both main and aftershocks (M≥4). The first earthquake was bilateral and ruptured a seismic gap along the East Anatolian Fault Zone, with rupture first propagating to the north-east for ~200 km, and in a latter phase propagating to the SSW, probably coming to a halt only on a branch extending into the Mediterranean Sea. The total length of the rupture likely exceeds 500 km. The second event ruptured the EW oriented Sürgü-Misis Fault Zone to the NW of the first event. It shows a highly concentrated rupture near the epicenter, Rupture directivity analyses for M≥5.3 earthquakes provide additional insights into dynamic source aspects. Preliminary moment tensor solutions of numerous aftershocks indicate a remarkable variability of rupturing mechanisms, suggesting stress changes and the activation of multiple faults in the vicinity of the main ruptures. With our work, we aim to shed light onto multiple aspects of the complex rupture evolution and hope to provide new insights towards a better understanding of the devastating 2023 Türkiye earthquake sequence.
The Shear Wave Velocity Structure of the Marmara Region by Using Receiver Function Analysis
AGU Fall Meeting Abstracts, Dec 1, 2012
The Seismic record, Apr 1, 2023
, southeastern Türkiye experienced two M w 7.7 and 7.6 earthquakes. The earthquake sequence cause... more , southeastern Türkiye experienced two M w 7.7 and 7.6 earthquakes. The earthquake sequence caused widespread damage and tens of thousands of casualties in Türkiye and Syria. We analyze mainshocks and aftershocks, combining complementary source characterization techniques, relying on local, regional, and teleseismic data. Backprojection analysis and finite source inversion for the mainshocks resolve coseismic slip, rupture length, and propagation mode along the main faults, whereas centroid moment tensor inversion for 221 aftershocks resolves details of the fault network. The first mainshock nucleated on a splay fault and activated the neighboring East Anatolian fault zone (EAFZ). It ruptured bilaterally along ∼500 km first toward northeast and later to south-southwest on multiple, previously partly dormant fault segments. The second mainshock ruptured the east-west-oriented Sürgü-Misis fault zone (SMFZ), reaching a slip of 7 m. The analysis of aftershocks with heterogeneous moment tensors retrospectively reconstructs rupture details. Along the main strand of the EAFZ, they map the geometry of different segments in unprecedented detail, whereas along the SMFZ they illuminate the geometry and behavior of large structures for the first time. Our work sheds light on multiple aspects of rupture evolution and provides new insights into the devastating earthquake sequence.
An atypical swarm at the North Mid-Atlantic ridge indicating spreading events
A large seismic swarm affected the North Mid-Atlantic ridge between September and November 2022, ... more A large seismic swarm affected the North Mid-Atlantic ridge between September and November 2022, with an outstanding seismicity rate and a cumulative moment equivalent to a magnitude Mw 6.3. We performed a detailed seismological analysis using regional, teleseismic and array data to reconstruct the spatiotemporal evolution of the seismicity. Combining template matching, relative location and full moment tensor inversion, we identify that most seismicity was located in a narrow band along the ridge, with typical normal faulting mechanisms. However, some of the latest and strongest events occurred up tp 25 km off the ridge axis, with thrust mechanisms that are atypical at mid-ocean ridges and inconsistent with the extensional tectonics. Seismicity also present a clear migration pattern, propagating over ~60 km from North to South, with the thrust mechanisms only occurring in the late phase of the swarm and only in the central-southern section. We hypothesize a magmatic intrusion as driver of the seismicity, with a vertical dyke first propagating southward, accompanied by normal faulting earthquakes, and then thickening, to produce a stress perturbation able to trigger thrust earthquakes on pre-existing structures on the side of the dike. The 2022 unrest provides evidence for sporadic spreading accompanied by large swarm episodes driven by magma intrusions at the mid-ocean ridge.
Moho Depth and Crustal Vp/Vs Variation in Marmara Region Obtained by Receiver Functions
2014 AGU Fall Meeting, Dec 16, 2014
Estimation of temporal seismic velocity changes associated with the 2008 Mt. Etna eruption from ambient noise cross-correlation
<p><br>On 13 May 2008, a strong eruption took place a... more <p><br>On 13 May 2008, a strong eruption took place along a fracture opened on Mt. Etna's eastern flank accompanied by significant seismic activity. Recent studies show that seismic ambient noise is an effective method to observe the fluctuations of seismic wave velocities due to volcanic and seismic activities. In this study, we analyze the temporal seismic velocity changes (<em>dv/v</em>) from January 2007 to June 2008 at Mt. Etna by using seismic ambient noise. We retrieve a large dataset to calculate <em>dv/v</em> because of the large number of permanent seismic stations located at Mt. Etna. Daily cross-correlation functions (CCFs) are computed at 15 stations for 105 interstation pairs in the 1-2 Hz frequency band by using vertical components. We observe that the <em>dv/v</em> displays a gradual reduction and reaches down to -0.3% associated with the aforementioned volcanic activity. We compared our results with volcano-tectonic earthquakes and volcanic tremor. Our study shows a significant relationship between the magma intrusion and decrease of the <em>dv/v</em>.</p>
Geophysical Journal International, Mar 21, 2018
Bodrum-Kos earthquake (M w 6.6) is the largest instrumentally recorded earthquake in the Gökova g... more Bodrum-Kos earthquake (M w 6.6) is the largest instrumentally recorded earthquake in the Gökova graben, one of the primary physiographic features of SW Turkey. Using seismology and satellite geodesy, we investigate its source characteristics, aftershock distribution, relationship with earlier instrumental seismicity, and association with known surface faulting. We show that the earthquake ruptured a planar (non-listric) normal fault that dips gently (∼37 •) northwards beneath the northern Gulf of Gökova coastline, initiating at a depth of ∼11 km and rupturing upwards and bilaterally. Aftershocks concentrate around (but not necessarily on) the western, eastern and downdip edges of the ∼25 km-long rupture plane, and have maximum focal depths of ∼15 km. The main shock surface trace bounds a bathymetric ridge east of Kos island, and may be one of the several faults imaged previously in this area using seismic profiling and multibeam sonar. The fault thus lies within the hangingwall of the lower-angle (∼20 • N-dipping) South Datça fault, which it presumably cross-cuts at depth. Through calibrated relocations, we confirm that sequences of moderate (M w 5-5.5) earthquakes in 1989, 2004 and 2005 occurred in the eastern and central Gulf of Gökova, many of them likely within the hangingwall of the S-dipping Gökova fault. Overall, our results indicate a switch from dominant S-dipping normal faulting in the eastern graben to dominant N-dipping faulting in the west, but we find no support for a proposed NE-SW-trending left-lateral fault in the central Gulf; most colocated focal mechanisms involve ∼E-W normal faulting. Finally, the Bodrum-Kos main shock adds to growing set of examples from across the Aegean region of large normal faulting earthquakes that cut the seismogenic layer as simple planar structures.
The Energetic 2022 Seismic Unrest Related to Magma Intrusion at the North Mid‐Atlantic Ridge
Geophysical Research Letters, Jul 6, 2023
Frontiers in Earth Science, Jun 14, 2021
Reservoir-triggered seismicity has been observed near dams during construction, impoundment, and ... more Reservoir-triggered seismicity has been observed near dams during construction, impoundment, and cyclic filling in many parts of the earth. In Turkey, the number of dams has increased substantially over the last decade, with Atatürk Dam being the largest dam in Turkey with a total water capacity of 48.7 billion m 3. After the construction of the dam, the monitoring network has improved. Considering earthquakes above the longterm completeness magnitude of M C = 3.5, the local seismicity rate has substantially increased after the filling of the reservoir. Recently, two damaging earthquakes of M w 5.5 and M w 5.1 occurred in the town of Samsat near the Atatürk Reservoir in 2017 and 2018, respectively. In this study, we analyze the spatio-temporal evolution of seismicity and its source properties in relation to the temporal water-level variations and the stresses resulting from surface loading and pore-pressure diffusion. We find that waterlevel and seismicity rate are anti-correlated, which is explained by the stabilization effect of the gravitational induced stress imposed by water loading on the local faults. On the other hand, we find that the overall effective stress in the seismogenic zone increased over decades due to pore-pressure diffusion, explaining the enhanced background seismicity during recent years. Additionally, we observe a progressive decrease of the Gutenberg-Richter b-value. Our results indicate that the stressing rate finally focused on the region where the two damaging earthquakes occurred in 2017 and 2018.
Journal Of Geophysical Research: Solid Earth, Oct 1, 2022
Mt. Etna-the tallest and most active stratovolcano in Europe-is one of the best monitored volcano... more Mt. Etna-the tallest and most active stratovolcano in Europe-is one of the best monitored volcanoes around the world since it is a natural laboratory for many disciplines (e.g., Bonaccorso et al., 2005; Patanè et al., 2013). On 24 December 2018, a flank eruption accompanied by an intense seismic activity took place and produced a dense rock equivalent (DRE) lava volume of about 2 Mm 3 (Figure 1; Laiolo et al., 2019). This volcanic crisis highlighted the importance of early warning systems to mitigate the potential damage in the surrounding settlements of Mt. Etna. Despite the significant improvements of technological progress and research, there still exists an uncertainty in forecast volcanic eruptions even with multi-parametric observations (e.g., Loughlin et al., 2015).
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Papers by Pinar Buyukakpinar