From low to high fidelity geophysics : 3-D multi-component shallow seismic surveying in the Lions' Harbour of Miletus (Turkey)

Wölz, Susanne

In this thesis a new high resolution 3-D multi-component seismic technique for shallow acquisition and interpretation was developed and evaluated. Unexplained linear and parallel magnetic anomalies, observed in the Lions' Harbour of Miletus (Turkey), correlate with the ancient street grid and raised the question if they could be related to quay wall or harbour foundations. Two 3-D multi-component refraction surveys were carried out in the alluvial sedimentary environment of this archaeological site, covering the magnetic structures. The use of Galperin geophones and the excitation of waves in three different directions led to 9-C datasets. Recorded wavefields show complex dynamic and kinematic behavior. Due to acquisition geometry and wavefield characteristics different phases of the wavefield intermix. Three different approaches to wavefield separation were defined and investigated, comprising a simple wavefield component rotation to geometric ray direction, calculation of curl and divergence at the surface and rotation into the ray coordinate system (''slowness projection''). The latter provides the best results for refracted arrivals. Extending the delay-time method to the 3-D case maps coherent basement structures on the meter-scale. The resulting model, a depth function of the refracting limestone horizon, was verified in depth by coring information and shows a minimum rms-error of 0.44 m with an average refractor depth of 10.5 m. Supplemental tomographic inversion results in a refined model showing surface velocity anomalies and a prominent high velocity zone in the refractor. The Milesian Lions' Harbour basin at this location is shallow enough and provides appropriate ground to found moles on solid rock.

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Wölz, Susanne: From low to high fidelity geophysics : 3-D multi-component shallow seismic surveying in the Lions' Harbour of Miletus (Turkey).

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