TY - JOUR A1 - Muksin, Umar A1 - Haberland, Christian A1 - Nukman, Mochamad A1 - Bauer, Klaus A1 - Weber, Michael H. T1 - Detailed fault structure of the Tarutung Pull-Apart Basin in Sumatra, Indonesia, derived from local earthquake data JF - Journal of Asian earth sciences N2 - The Tarutung Basin is located at a right step-over in the northern central segment of the dextral strike-slip Sumatran Fault System (SFS). Details of the fault structure along the Tarutung Basin are derived from the relocations of seismicity as well as from focal mechanism and structural geology. The seismicity distribution derived by a 3D inversion for hypocenter relocation is clustered according to a fault-like seismicity distribution. The seismicity is relocated with a double-difference technique (HYPODD) involving the waveform cross-correlations. We used 46,904 and 3191 arrival differences obtained from catalogue data and cross-correlation analysis, respectively. Focal mechanisms of events were analyzed by applying a grid search method (HASH code). Although there is no significant shift of the hypocenters (10.8 m in average) and centroids (167 m in average), the application of the double difference relocation sharpens the earthquake distribution. The earthquake lineation reflects the fault system, the extensional duplex fault system, and the negative flower structure within the Tarutung Basin. The focal mechanisms of events at the edge of the basin are dominantly of strike-slip type representing the dextral strike-slip Sumatran Fault System. The almost north south striking normal fault events along extensional zones beneath the basin correlate with the maximum principal stress direction which is the direction of the Indo-Australian plate motion. The extensional zones form an en-echelon pattern indicated by the presence of strike-slip faults striking NE SW to NW SE events. The detailed characteristics of the fault system derived from the seismological study are also corroborated by structural geology at the surface. (C) 2014 Elsevier Ltd. All rights reserved. KW - Focal mechanism KW - Seismicity KW - Structural geology KW - Extensional duplex KW - Flower structure KW - Sumatran fault KW - Pull-Apart Basin Y1 - 2014 U6 - https://doi.org/10.1016/j.jseaes.2014.09.009 SN - 1367-9120 SN - 1878-5786 VL - 96 SP - 123 EP - 131 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Braeuer, Benjamin A1 - Asch, Günter A1 - Hofstetter, Rami A1 - Haberland, Christian A1 - Jaser, D. A1 - El-Kelani, R. A1 - Weber, Michael H. T1 - Detailed seismicity analysis revealing the dynamics of the southern Dead Sea area JF - Journal of seismology N2 - Within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. During 18 recording months, 648 events were detected. Based on an already published tomography study clustering, focal mechanisms, statistics and the distribution of the microseismicity in relation to the velocity models from the tomography are analysed. The determined b value of 0.74 leads to a relatively high risk of large earthquakes compared to the moderate microseismic activity. The distribution of the seismicity indicates an asymmetric basin with a vertical strike-slip fault forming the eastern boundary of the basin, and an inclined western boundary, made up of strike-slip and normal faults. Furthermore, significant differences between the area north and south of the Bokek fault were observed. South of the Bokek fault, the western boundary is inactive while the entire seismicity occurs on the eastern boundary and below the basin-fill sediments. The largest events occurred here, and their focal mechanisms represent the northwards transform motion of the Arabian plate along the Dead Sea Transform. The vertical extension of the spatial and temporal cluster from February 2007 is interpreted as being related to the locking of the region around the Bokek fault. North of the Bokek fault similar seismic activity occurs on both boundaries most notably within the basin-fill sediments, displaying mainly small events with strike-slip mechanism and normal faulting in EW direction. Therefore, we suggest that the Bokek fault forms the border between the single transform fault and the pull-apart basin with two active border faults. KW - Dead Sea basin KW - Microseismicity KW - Cluster KW - Pull-apart basin KW - Asymmetric basin KW - Transform fault Y1 - 2014 U6 - https://doi.org/10.1007/s10950-014-9441-4 SN - 1383-4649 SN - 1573-157X VL - 18 IS - 4 SP - 731 EP - 748 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Vales, Dina A1 - Dias, Nuno A. A1 - Rio, Ines A1 - Matias, Luis A1 - Silveira, Graca A1 - Madeira, Jose A1 - Weber, Michael H. A1 - Carrilho, Fernando A1 - Haberland, Christian T1 - Intraplate seismicity across the Cape Verde swell: A contribution from a temporary seismic network JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008. The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antao and Sao Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antao, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde. The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record. (C) 2014 Elsevier B.V. All rights reserved. KW - Intraplate seismicity KW - Clustering KW - Local magnitude scale KW - Active volcanism KW - Cape Verde KW - Atlantic Ocean Y1 - 2014 U6 - https://doi.org/10.1016/j.tecto.2014.09.014 SN - 0040-1951 SN - 1879-3266 VL - 636 SP - 325 EP - 337 PB - Elsevier CY - Amsterdam ER -