The existing research shows that the immersed tunnel is significantly affected by the earthquake, but the damage will cause serious casualties and property damage, and it is difficult to repair. However, the shaking table test of immersed tunnel including seabed and seawater site is difficult to realize at present, and numerical simulation is generally used for analysis. It has been found that seawater layer, seabed site conditions and soil-structure interaction have a large effect on the seismic response of immersed tunnels, but most of the existing studies have used two-dimensional models to analyze. In order to determine the influence of three-dimensional seabed site on the seismic response of immersed tunnel. Firstly, a three-dimensional layered site wave analysis program was established by using the coordinate system transformation and transfer matrix method, and combined with the finite element dynamic analysis software, a three-dimensional seismic wave analysis method of seawater and seabed immersed tunnel coupling was proposed. Besides, the correctness of the method is verified, and the influence of multi-dimensional site characteristics on seismic response of seabed site is analyzed. Finally, the immersed tunnel of Hong Kong-Zhuhai-Macao Bridge in China is taken as an engineering example, and the effects of tunnel longitudinal slope, incidence angle of ground motion, thickness of soft soil layer and water depth on seismic response analysis are studied. The results show that there is a great difference between twodimensional and three-dimensional seabed site model in seismic response. When considering the soft soil layer, the vertical seismic response of three-dimensional seabed site is significantly greater than that of twodimensional seabed site.Moreover, the silty soft soil layer also has a significant effect on the seismic response of the immersed tunnel, there is an obvious amplification effect on the tunnel horizontal seismic response. Besides, the horizontal seismic response of tunnel will be amplified with the increase of tunnel longitudinal slope and incidence angle, while the seismic response of tunnel will be inhibited with the increase of seawater depth.

Landslides, one of the natural disaster problems, occur due to slope stability triggered by natural or human activities. Once such mass movements have begun, they are challenging to stop and, in some cases, almost impossible. Geophysical methods are very effective in determining the character and mechanical properties of landslides with a high resolution before or after mass movement. This study aims identifying the landslide that tends to continue in the & Ccedil;aml & imath;ca neighborhood of the Hendek district of Sakarya province by electrical resistivity (ERT), surface waves analysis (MASW-ReMi), and mechanical soil drilling. The low resistivity and low shear wave velocity (Vs) unit in the geophysical sections was determined as a saturated clayey thick cover layer from the borehole log. This clayey unit causes mass movement on the slip surface. Andesite-basalt-containing bedrock unit under the slip surface has been identified as having high resistivity and high velocity in geophysical sections. The integrated use of geophysical methods in this landslide, determined as the progressive mechanism, contributed significantly to the realistic modeling of the landslide internal structure.

Permafrost degradation is rapidly increasing in response to a warming Arctic climate, altering landscapes and damaging critical infrastructure. Solutions for monitoring permafrost thaw dynamics are essential to understand biogeochemical feedbacks as well as to issue warnings for hazardous geotechnical conditions. We investigate the feasibility of permafrost monitoring using permanently installed fiber-optic seismic networks. We conducted a 2-month seismic monitoring campaign during a controlled thaw experiment using a permanent surface orbital vibrator (SOV) and a 2D-array of distributed acoustic sensing (DAS) cables, and observed significant (15%) shear-wave velocity (V-s) reductions and approximately 2 m depression of the permafrost table beneath the heating zone. These observations were validated by time-lapse horizontal-to-vertical spectral ratio (HVSR) analysis from three co-located broadband seismometers. The combination of SOV and DAS provided unique seismic observations for permafrost monitoring at the field scale, as well as a basis for design and development of early warning systems for permafrost thaw.