Surface Manifestation Of Liquefaction Research Articles

Geotechnical reconnaissance findings of the October 30 2020, Mw7.0 Samos Island (Aegean Sea) earthquake

On October 30, 2020 14:51 (UTC), a moment magnitude (Mw) of 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea north of the island of Samos, Greece. Turkish and Hellenic geotechnical reconnaissance teams were deployed immediately after the event and their findings are documented herein. The predominantly observed failure mechanism was that of earthquake-induced liquefaction and its associated impacts. Such failures are presented and discussed together with a preliminary assessment of the performance of building foundations, slopes and deep excavations, retaining structures and quay walls. On the Anatolian side (Turkey), and with the exception of the Izmir-Bayrakli region where significant site effects were observed, no major geotechnical effects were observed in the form of foundation failures, surface manifestation of liquefaction and lateral soil spreading, rock falls/landslides, failures of deep excavations, retaining structures, quay walls, and subway tunnels. In Samos (Greece), evidence of liquefaction, lateral spreading and damage to quay walls in ports were observed on the northern side of the island. Despite the proximity to the fault (about 10 km), the amplitude and the duration of shaking, the associated liquefaction phenomena were not pervasive. It is further unclear whether the damage to quay walls was due to liquefaction of the underlying soil, or merely due to the inertia of those structures, in conjunction with the presence of soft (yet not necessarily liquefied) foundation soil. A number of rockfalls/landslides were observed but the relevant phenomena were not particularly severe. Similar to the Anatolian side, no failures of engineered retaining structures and major infrastructure such as dams, bridges, viaducts, tunnels were observed in the island of Samos which can be mostly attributed to the lack of such infrastructure.

Cyclic and monotonic simple shear testing of native Christchurch silty soil

The first cyclic simple shear tests on high-quality retrieved specimens of Christchurch silty and sandy soil were performed to evaluate their liquefaction potential. The test specimens originate from stratified silty soil deposits in southwestern Christchurch which did not typically have surface manifestations of liquefaction after the intense shaking of the 2011 Christchurch earthquake. The soil's undrained cyclic stress-strain responses indicate cyclic mobility. The differences in the cyclic responses of the soil with different amounts of non-plastic silt are subtle. Specimens with greater cyclic stiffness degradation typically had lower post-cyclic stiffness. The soil stiffness was significantly lower in post-cyclic tests than in monotonic tests due to the large differences in the initial effective stresses between the two types of tests, loss of strength, age, and fabric effects. The field-adjusted laboratory-based cyclic resistances agree with CPT-based cyclic resistances from simplified liquefaction triggering procedures. Both assessments indicate the silty soil deposits generated high excess pore water pressures and liquefied during the Christchurch earthquake even though surface manifestations of liquefaction were not typically observed at the considered sites. The absence of liquefaction manifestation at the stratified silty soil sites highlights the importance of their system response.

Intensity estimation for the 2001 Bhuj earthquake, India on ESI-07 scale and comparison with historical 16th June 1819 Allah Bund earthquake: A test of ESI-07 application for intraplate earthquakes

On 26th January 2001, an earthquake of magnitude Mw 7.7 occurred near Bhuj, in northwestern India, resulting in severe environmental effects. No unequivocal primary surface rupture was observed for the earthquake, but it caused widespread liquefaction and lateral spreading in the Rann of Kachchh and Little Rann. After the earthquake, several researchers collected field evidence of secondary surface rupture, rockfall, dry craters, and surface manifestations of liquefaction, including the formation of mud volcanoes and lateral spreads, in the meizoseismal area. Analysis of pre- and post-earthquake satellite images suggests that several “dry” streams in the Rann of Kachchh began to flow due to extensive liquefaction induced by the earthquake. In this present study, the macroseismic intensity of the Bhuj earthquake is evaluated by considering these environmental effects and applying the ESI-07 intensity scale to the affected area. As an outcome, the epicentral intensity of the 2001 Bhuj earthquake was determined to be XI. According to historical records and seismic catalogs, 16th June 1819 Allah Bund earthquake caused prominent surface rupture which was not so clear in the case of 2001 Bhuj earthquake, but the secondary effects were similar for both earthquakes. Considering the environmental effects caused by the 1819 Allah Bund earthquake, an intensity of XI was estimated for the epicentral area. For both earthquakes, the ESI scale yields a significant difference of one to two degrees with the traditional intensity scales. The 2001 Bhuj earthquake and 1819 Allah Bund earthquake shows similar ESI-07 intensity of XI despite of different epicentral locations. This implies the reliability of ESI-07 scale application for different earthquakes of similar dimensions in the same geological setting. This study contributes to the application of ESI-07 scale for Indian earthquakes, especially reverse faulting events, and to the future improvement of the ESI scale with emphasis on its applicability to historical earthquakes on the Indian subcontinent. Also, this study may help in future land use planning in the meizoseismal area of 1919 Allah Bund and 2001 Bhuj earthquakes.

Secondary effects generated by earthquakes: liquefaction occurrences in and around Hungary

Soil liquefaction have been observed and documented at least eight times during moderate to larger magnitude historical and recent earthquakes in Hungary. Surface manifestations of liquefaction were reported from Komárom (1763, 1783, 1822), Mór (1810), Érmellék (1829, 1834), Kecskemét (1911) and Dunaharaszti (1956) earthquakes. In the study, we give a brief description of these earthquakes and make available reports that demonstrate the occurrence of soil liquefaction. Where available, we describe local subsoil conditions and information regarding ground water level. Distribution of horizontal ground accelerations possibly caused by these historical earthquakes has been modelled by ShakeMap program. Simulations indicate horizontal PGA of 0.2–0.3 g in areas where liquefaction occurred.

Liquefaction Hazard Assessment of Earth Quake Prone Area: a Study Based on Shear Wave Velocity by Multichannel Analysis of Surface Waves (MASW)

The shear wave velocity (VS) profile based on the dispersive characteristics of fundamental mode of Rayleigh type surface waves indicate underground stiffness change with depth as well as near surface stiffness. The most important utility of shear wave velocity (VS) is to estimate the liquefaction hazard potential of an area particularly in seismically active region. Rayleigh type surface waves were utilized to estimate the velocity (VS) of shallow subsurface covering a depth range of 30–50 m employing multichannel analysis of surface waves. The liquefaction hazard map predicts an approximate percentage of an area that will have surface manifestation of liquefaction during an earth quake. The surface wave data acquired in an earth quake prone region of Jabalpur (Seismic zone III), India, yields a velocity (VS) range of 200–750 m/s corresponding to the subsurface depth of 30–35 m. The results were analyzed for possible liquefaction hazard in the study area and presented here besides the N values.

Seismic Response of Soil Deposits in San Francisco Marina District

This paper presents an application of the effective stress based, fully coupled, nonlinear numerical procedure DYSAC2 and the total stress-based, equivalent-linear procedure SHAKE to the analysis of the seismic response of soil deposits in the San Francisco marina district. A dynamic centrifuge model test was performed using subsurface conditions similar to those found in the marina district to evaluate the predictions made by DYSAC2 and SHAKE. Three sites in the marina district were selected for site investigations and analyses. The first site showed no indications of soil liquefaction and no building damage. The second site showed no indication of liquefaction either, yet considerable building damage was observed in the vicinity. At the third site, surface manifestations of liquefaction were observed in addition to considerable damage to neighboring buildings. The dynamic behavior of these three sites was evaluated using DYSAC2 and SHAKE. The results of this analysis are presented and are compared to the observed behavior in the marina district during the Loma Prieta earthquake. Discrepancies between the DYSAC2 and SHAKE predictions are also discussed.

Liquefaction-Induced Ground Damage in Dagupan in the July 16, 1990 Luzon Earthquake

ABSTRACT Geotechnical aspects of the ground damage caused by widespread occurrence of liquefaction at the time of the 1990 Luzon, Philippines earthquake are highlighted by examining the geomorphological regime and boring data obtained in the city area of Dagupan. The comparison of old and present locations of the river courses indicates that the liquefaction in the city of Dagupan had taken place in two geomorphologically different areas: namely, the terrain of naturally buried old river channels and the area of point bar deposits. Although impossible to distinguish soil profile characteristics between these two types of terrains, the common feature is that there exists a surface layer composed of unliquefiable silty soils, underlain by sand deposits which are loose enough to provoke liquefaction. As a result of simple analysis of liquefaction, it was shown that the upper part of this sand deposits developed liquefaction, leading to the disastrous consequences in the city of Dagupan. By compiling a number of SPT data and the data of Swedish cone penetration tests, an attempt was made to clarify the relationship between the thickness of unliquefiable surface layer and that of the underlying liquefied layer which can or can not bring about surface manifestation of liquefaction, accompanied by disastrous damage on the ground surface. Lastly, the lateral spreads of the ground near the riverside were analyzed by considering the soil profiles established by the Swedish cone tests. The residual strength determined by back-calculation at three typical cross sections indicated a general coincidence with those estimated previously for other data sets.