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  • [ X ]
    Öğe
    Geothermal gradients and seismicity correlations in the Biga Peninsula (NW Türkiye) based on Curie point depths
    (Inst Geology & Geography, 2025) Bektas, Ozcan; Buyuksarac, Aydin; Pamuk, Eren; Canbaz, Oktay
    The Biga Peninsula has hot springs with geothermal temperatures varying between 40oC and 175oC. In this study, we investigate the regional temperature distribution and change in radiogenic heat production in the Biga Peninsula. We use EMAG2 magnetic data to estimate the Curie point depth (CPD). Our findings show that the CPD in the region varies between 9 km and 17 km. We also calculated the geothermal gradient and heat flow values based on the CPD data. which range between 92.9 and 141.6 mWm-2. Additionally, we also obtained values for zo, zt, and zbfrom the power spectrum and calculated 1D geothermal gradient change for examined blocks. The resulting equations are: zt= z80 degrees C, zo= z350 degrees C, and zb= z580 degrees C. These equations enabled us to propose a new formula to calculate the CPD. We also obtained the Conrad discontinuity depth (zc = z680 degrees C) in the Biga Peninsula. Furthermore, we prepared 2D heat flow and temperature profiles along three sections to investigate the relationship between heat changes and earthquake focal distributions. The results indicate that seismicity is high in the southwest of the Biga Peninsula, which has a high CPD, high heat flow value, and shallow Conrad discontinuity.
  • [ X ]
    Öğe
    Shear-wave velocity model of the Sivas City (inner eastern, Türkiye) using Rayleigh wave ellipticity inversion controlled by 2D microgravity modeling
    (Springer Int Publ Ag, 2025) Bektas, Ozcan; Buyuksarac, Aydin; Saritepe, Halil Erdim; Onal, Kemal Mert; Canbaz, Oktay; Eyisuren, Onur; Pamuk, Eren
    The change in duration, amplitude, and frequency content of the earthquake ground motion as it passes through the rock and ground environment is referred to as the local ground effect. Impedance differences between bedrock and soil, as well as the dynamic behavior of soils, can amplify this effect. The geometry of both dense and loose soil layers must be known to accurately define soil-structure interaction and properly assess how soil behavior affects a structure during an earthquake. Local ground effects are known to play a significant role in structural damage during earthquakes. In basin-like environments, however, studies based on foundation and sub-base depth often lack sufficient information, making it difficult to identify problems associated with basin effects. It is not appropriate to provide construction-related information, especially in environments with a basin structure like Sivas, without determining the bedrock or solid ground conditions. This study aimed at determining the bedrock/seismic foundation depth for the central settlement of Sivas and defining the basin structure, involved large-scale microgravity measurements. The study area was modeled in three dimensions using the gravity data obtained. Long-term microtremor measurements were also conducted, and one-dimensional depth-shear-wave (Vs) velocity models were generated using the Rayleigh ellipticity method. The bedrock/seismic foundation structure of the study area was defined using two different methods, and these definitions were combined into two-dimensional sections. A depth map of the study area was created, revealing that the thickness of the loose basin unit is approximately 90 m. Ambient noise was recorded at 35 points with a velocity seismometer, and S velocity (Vs) profiles were obtained from joint inversion of Rayleigh ellipticity data and dispersion curves from MASW and ReMi data. Furthermore, the Vs-depth structure of the basin was defined along the profiles cutting the basin in NW-SE and S-N directions, based on the Vs velocities in the 2D gravity model. The frequency range along these profiles was found to be 0.6 Hz in the deep parts of the basin and 2.5 Hz in the shallow parts.