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Crustal velocity structure in Borneo Island using receiver function inversion

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Syuhada S. , Pranata B. , Anggono T. , Ramdhan M. , Zulfakriza Z. , Febriani F. , Prasetio A. D. , Dewi C. N. , Hasib M. , Sulaiman A.

Acta Geophysica

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2022

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tom Vol. 70, no 6

2529--2553

EN

Borneo is an island situated in a tectonically complex region and characterised by multiple arcs and continental blocks accreted during the Mesozoic and early Cenozoic. We analyse receiver functions of teleseismic events from 12 seismic stations around the island. In general, these stations sample a variety of geological environments, including Meratus Complex, Eastern Borneo, South–Western Borneo, North–Western Borneo, and Sabah Zones. We then derive the shear wave velocity models from the inversion of receiver functions using the stochastic non-linear approach. Inversion results indicate that the island is covered by sedimentary layers with thickness ranging from 1 to 3 km thick. The inversion solutions for most stations also show that the crustal thickness varies between 26 and 36 km around the region. The variation in the average crustal Vp/Vs values obtained for each seismic station addresses the geological diversity of the study area. Furthermore, the lowvelocity zone with high and low Vp/Vs in the lower crust observed beneath some seismic stations may be associated with the tectonic evolution and development of Borneo Island. The results inferred from our inversion are generally consistent with other previous geological and geophysical studies conducted in this region.

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Structure of the crust and lithospheric mantle beneath the central main Ethiopian rift

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Kassa M. , Alemu A. , Muluneh A.

Acta Geophysica

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2022

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tom Vol. 70, no 5

1979--1999

EN

We use the complete Bouguer anomaly (CBA) derived from GGMplus 2013 to model the lithosphere–asthenosphere boundary (LAB) depth, LAB temperature, lithospheric mantle density and crustal/lithospheric mantle structure of the central main Ethiopian rift (CMER) and surrounding regions. The regional Bouguer anomaly is estimated by using a 200-km cutoff wavelength low-pass filter, and the resulting anomaly map is inverted using Parker–Oldenburg method to generate the depth to the LAB. The result shows that the LAB depth values fluctuate between 38.8 and 78 km in the region. The LAB temperature is estimated based on the results of the LAB depth in the CMER and surrounding regions. The LAB temperature estimates range between 1267 and 1287 °C in the region. The lithospheric mantle density in the study area varies from 3240 to 3295 kg/m3 , as estimated using empirical equations. Relatively low lithospheric mantle densities are determined to occur beneath the Yerer-Tullu-Wellel Volcanotectonic Lineament and Boru-Toru Structural High. 3D gravity models computed for the study area show thickening of the bottom interfaces of the top layer, upper and lower crystalline basement depths when going from the rift toward the western and eastern plateaus. This crustal thickening is evidenced by the associated low CBA (approximately−285 mGal) observed over the plateaus.

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Badania struktury skorupy ziemskiej na obszarze Europy Centralnej, ze szczególnym uwzględnieniem Transeuropejskiej Strefy Szwu, metodami głębokich profilowań sejsmicznych

51%

Guterch A.

Wiadomości Naftowe i Gazownicze

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2012

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tom R. 15, Nr 9 (173)

4--9

EN

The complex tectonic history of Central Europe (Fig. 1a) reflects the break-up of a Neoproterozoic supercontinet(s) (Rodinia/Pannotia) to form the fragment Baltica and the subsequent growth of continental Europe beginning with the Caledonian orogeny. Caledonian and younger Variscan orogenesis involved accretion of Laurentian and Gondwanan terranes to the riftet margin of Baltica. (East European craton, EEC) during the Paleozoic. From Central Poland northward, the region also experienced volcanic activity during the Permian and tectonic inversion during the Alpine orogeny, which in the south continues today. The Trans-European Suture Zone (TESZ) is a term used to refer to the suite of sutures and terranes that formed adjacent to the rifted margin of Baltica, and these features extend from the British Isles to the Black Sea region (Fig. 1a and 2). Understanding the structure and evolution of the TESZ region is one of the key tectonic challenges in Europe north of the Alps. The TESZ is far more complex than a single suture but in a broad sense is the boundary between the accreted terranes and Baltica. The TESZ includes the Teisseyre-Tornquist Zone (TTZ), which has several definitions. Here, we will use the term TTZ to refer to a structural zone associated with the southwestern edge of the EEC. Beginning in 1997, Central Europe, between the Baltic and Adriatic Seas, has been covered by an unprecedented network of seismic refraction experiments (Fig. 1b). These experiments - POLONAISE’97, CELEBRATION 2000, ALP 2002, and SUDETES 2003 - have only be possible due to a massive international cooperative effort. International Consortium consisted of 35 institutions from 16 countries in Europe and North America - Austria, Belarus, Canada, Croatia, Czech Republic, Denmark, Finland, Germany, Hungary, Lithuania, Poland, Russia, Slovakia, Slovenia, Turkey and the United States. The majority of the recording instruments was provided by the IRIS/ PASCAL Instrument Center and the University of Texas at El Paso (USA), the Geological Survey of Canada and other countries. For example, in the CELEBRATION experiment, the total number was 1230 stations ands 147 shot points located along seismic lines of a total length of about 9000 km. A large number of seismic sources and stations in all experiments means that besides 2 - D approach along profiles (Fig. 3 and 4), also 3 - D approach (Fig. 5 and 6) could be implemented in data interpretation. Total length of seismic profiles in all experiments is about 20 000 km (Fig. 1b).