Liquefaction-induced lateral spreading at Izmit Bay during the 1999 Kocaeli (Izmit) – Turkey Earthquake

This paper presents a study of liquefaction-induced lateral ground displacements along the coast of Izmit Bay during the 1999 Kocaeli (Izmit)-Turkey earthquake. The paper discusses: (1) observed ground displacements after the earthquake, (2) the results of field investigations by means of borings and in situ index tests, including standard penetration tests, static cone penetration tests, and piezocone tests, (3) analyses of expected lateral displacements using two empirical models and one semiempirical model, and (4) comparisons between observed and calculated lateral ground movements. The three models provide inconsistent predictions of observed lateral ground displacements, with one method overpredicting and two methods both overpredicting and underpredicting observed lateral ground displacements by large amounts. Thus, it appears that there is a need for improved engineering tools for prediction of small to moderately significant lateral ground displacements (lateral displacements of approximately 0.1−2.5m) at soil sites with similar ground characteristics to the case history sites presented herein

Influence of releasing step-overs on surface fault rupture and fault segmentation: Examples from the 17 August 1999 Izmit earthquake on the North Anatolian fault, Turkey

The 17 August 1999 Izmit earthquake broke four distinct structural segments of the North Anatolian fault, from east to west: the Karadere, Sakarya, Sapanca, and Golcuk fault segments. These segments are separated from one another and the adjoining Yalova and Duzce fault segments to the west and east, respectively, by distinct right-releasing step-over and/or gaps in the fault trace. These include, from east to west, the Eften Lake step-over (2-4 km wide), Akyazi gap (6-13 kin long), Sapanca step-over (1-2 km wide), Golcuk step-over (1-2 kin wide), and Karamursel step-over (4-5 kin wide). The earthquake nucleated within or near the Golcuk step-over with bilateral rupture propagation to the west and east. To the west, about 4-5.5 m of surface rupture (up to 7 in of subsurface rupture) on the Golcuk segment was mostly, if not entirely, arrested by the 4- to 5-km-wide Karamursel step-over. To the east, about 3-4 in of surface rupture (about 4 m of subsurface rupture) propagated through the 1- to 2-km-wide Sapanca step-over, triggering up to 4.5-5.5 in of surface rupture (up to 5-6 m of subsurface rupture) on the Sakarya segment. Rupture on the Sakarya segment stepped across the Akyazi gap triggering 1-1.5 in of rupture on the Karadere segment. Rupture on the Karadere segment was arrested by the 2- to 4-km-wide Eften Lake step-over

Liquefaction-induced ground deformations at Hotel Sapanca during Kocaeli (Izmit),Turkey earthquake

This paper presents a study of liquefaction-induced ground deformations at the Hotel Sapanca site during the 1999 Kocaeli (Izmit)-T Turkey earthquake. The paper discusses: (1) observed ground deformations and displacements after the earthquake, (2) the results of field investigations by means of borings and in situ index tests including standard penetration tests (SPT), static cone penetration tests (CPT) and piezocone (CPTU) tests, (3) analyses of observed ground settlements and lateral deformations by a suite of methods, and (4) comparisons of observed and calculated ground movements

Post Earthquake Aggradation Processes to Hide Surface Ruptures in Thrust Systems: The M8.3, 1934, Bihar‐Nepal Earthquake Ruptures at Charnath Khola (Eastern Nepal)

International audienceThe Charnath Khola is a large river crossing the Himalayan thrust system in the region devastated by the great M8.3 1934 Bihar-Nepal earthquake. Fluvial terraces are abandoned along the river and at the base of a~20-m high cumulative thrust escarpment. A trench across the fault scarp exposed Siwalik mudstone/siltstone overthrusting Quaternary units and three colluvial wedges interfingered with fluvial sands. The 85 accelerator mass spectrometry radiocarbon dates, from detrital charcoals sampled in the trench, a river cut and river terraces, constrain the timing of the sedimentary processes following the last two major earthquakes, in 1934 and 1255 CE. Although several samples straddle the main earthquake horizon, associating it with the 1934 earthquake, based solely on radiocarbon ages, remains challenging. The 49 detrital charcoal ages found in the pre-earthquake and postearthquake units fall between 65 and 225 BP, a period with a flat calibration curve. Many of these radiocarbon ages are suspected to include a part due to inbuilt time (i.e., age of the wood at the time of burning), transport time, and reworking processes, which are difficult to resolve. Considering these ages at their face value could lead to dates older than the actual earthquake dates. We suggest that a part of this chronological bias is also related to a local postseismic aggradation pulse of 4 to 5 m of sediments, which is documented in the trench and terraces. This fluvial sequence, hiding the most recent surface rupture, is likely related to landslide-sediment deposition triggered by the 1934 Bihar-Nepal earthquake