Where is creep especially active

Emergency Management. Survey Manual. Creep is steady fault movement, varying from continuous to episodic with creep events lasting minutes to days. Generally creep occurs without any associated earthquake activity i. Creep has been monitored on the Hayward fault for fifty years Lienkaemper et al. How deep does creep go? How can a creeping Hayward fault still produce major earthquakes? The short answer is that the depth of creep varies, from as little 2 miles deep in northern Oakland to as deep as 7 miles near the northern and southern ends of the fault.

Unfortunately, this means the lower, brittle fault zone remains largely locked i. The average recurrence time for earthquakes is determined by paleoseismologists, geologists who work in trenches across the faults.

They document evidence of paleoearthquakes recorded in sedimentary layers, using radiocarbon analysis to date them. User Tools. Sign In. Advanced Search. Skip Nav Destination Article Navigation.

Close mobile search navigation Article navigation. Volume 39, Number Previous Article Next Article. Article Navigation. Research Article December 01, Gratier ; J. Google Scholar. Richard ; J. Renard ; F. Mittempergher ; S.

The along-slope projection is discussed in Colesanti and Wasowski and Cascini et al. Figure 9 shows the map of cumulative displacements over the entire observed period from December to October In this case, the values were projected in the direction of the steepest slope. The displacement time series are discussed later in this paper.

LOS displacement velocity map of the study area period of observation: — This figure approximately covers the same area shown in Fig. Cumulative displacement map of the study area obtained from PSI period of observation: — The LOS displacement was projected along the steepest slope direction. This occurs in the two sectors shown in Fig. Figure 9 shows displacements in El Papiol and Les Escletxes hills. Between these two hills there is a slope that includes the Parc Central area.

It is worth recalling that the PSs basically cover the built-up areas, whereas in the areas of vegetation, there are no PSs. Based on the results shown in Fig. Most of the PSs are green, indicating zero or negligible displacements below 10 mm in the 5-year observed period.

The PSs that show displacement are concentrated on the slopes that belong to the Les Argiles Creek basin. There are some isolated orange or red PSs in the green zones, some of them located in flat areas. It must be borne in mind that isolated displacements may not be due to terrain instability, but rather to very local displacements of light poles, other metallic elements, or single buildings.

Seven main sectors have been identified in the displacement-affected zones see Fig. The PSs, with displacements up to 50 mm, are located in a rather flat area over houses built in the same period. There is no evidence of instability resulting from the or episodes.

After an in situ observation, the displacement of this sector was judged to be due to causes other than soil creep, e. For this reason, this sector was not further considered in this work. This sector suffered displacements in Some damage is still visible Fig. This sector coincides with a sliding area that occurred during the and episodes. Its displacements range from 50 to 80 mm. Sector D: Set of buildings located below Parc Central.

The major damages occurred in this sector in Fig. The displacements range from 15 to mm. This sector was urbanised after , and therefore, there are no historical damage records. The displacements range from 20 to 40 mm. Sector F: Football pitch retaining wall, showing some pathologies.

This sector was urbanised after The displacements range from 40 to mm. Sector G: New houses located above the football pitch, which show no pathologies.

This sector, which was urbanised after , has displacements between 30 and 70 mm. Figure 10 shows the displacement time series estimated using PSI over the above sectors. The time series refer to single PSs located in each sector.

The time series of Sector A show displacements up to 80 mm. However, in this sector, the ratio between the displacements projected parallel to the local slope and the original LOS values is this amplification factor makes the values of the time series unreliable; see Colesanti and Wasowski , Cascini et al. For this reason, the time series for sector A are not shown in Fig.

Sectors B, E, F and G show displacements with similar magnitudes over time. Sector C shows three types of displacements over time: an initial period with a moderate downward displacement rate, followed by a second period with no apparent displacement, and a final period with a slow upward displacement.

This could be related to the different stabilisation works of the road retaining wall. Sector D shows the biggest displacements. In general, the displacements of the time series are not continuous: they are irregular, mainly due to the noise and atmospheric component of the PSI observations Crosetto et al.

Times series showing the temporal evolution of displacements on the seven sectors selected from B to G in Fig. The displacement is projected on the direction of the steepest slope direction. The above figure, which corresponds to sector B, shows cumulative displacements of about 50 mm and two patterns: from 0 to days, there is a moderate displacement rate, while in the second period observed, the rate is higher and rather constant.

Note that the time series show some spikes, which are probably due to residual atmospheric effects. The middle figure sector D displays a cumulative displacement of mm and a pattern similar to the previous figure: a moderate displacement rate between 0 and , followed by a period with a higher displacement rate.

The figure below shows a cumulative displacement of up to mm, which has a rather constant rate over the entire observed period. Displacement time series represented by lines versus precipitation. In all plots, each bar represents 1 month. Bars in dark blue represent the maximum rainfall received in 1 day on a monthly basis, while the bars in light blue represent the total monthly rainfall. For superficial landslides, activation or acceleration may depend on surface water due to rain, rather than the piezometric groundwater level.

To assess the effect of heavy rain on the activity of El Papiol soil creep, the displacement time series were compared with the rainfall records. Using the data published by the Catalan Meteorological Service www. One may notice that the displacement rates are not correlated with the cumulative monthly rainfall or the maximum daily rainfall per month.

It is worth comparing the rainfall records of — with those from and This is useful to analyse the effectiveness of the measures taken from administrations to cope with the damaging instability. Unfortunately, the Castellbisbal weather station began keeping its records in Therefore, we used the nearest available station with rainfall records starting in , located at the Barcelona Airport, about 12 km away from El Papiol, which is managed by the Spanish Weather Agency www.

Considering the month of November, the highest daily rainfall was on November 7, , with Therefore, considering the entire recorded period, both December and November rainfall events represent extreme episodes.

The total rainfall of these events was sufficient to trigger or accelerate the instability. By contrast, the rainfall registered in the — period was insufficient to activate the instability.

A spatial analysis of instability was performed using geomorphological and geological information, historical records and the PSI data. The procedure involved two stages. In the first one, the unstable areas were identified, while in the second one, these areas were classified according to their activity. The unstable zones correspond to areas where the underlying geology and the topography make them prone to instability in the form of soil creep.

This information was compared with the results from PSI. The detrital material from Miocene, Pliocene and Quaternary formations B, D and E was considered to be potentially favourable to cause instability.

In fact, the alteration of these materials gives rise to a superficial formation that becomes unstable. From the areas with the above materials, we discarded those that show morphological traces associated with stability, e. The Les Escletxes zone was added to the potentially unstable areas due to the wide cracks of this area.

All remaining parts of the areas were considered stable. The classification of the unstable zones was done according to Cooper , using four classes: active, dormant, stabilised and relict see Table 1 and Fig. Landslide activity map according to the classification by Cooper obtained from a geomorphological evidence found in the studied area, b historical instability records, c PSI results and d geological information. Materials under service conditions are required to sustain steady loads for prolonged periods of time and often undergo a time-dependent deformation that is referred to as creep resistance.

Creep is the natural tendency of a material to gradually move or permanently deform as a result of mechanical stress or strain. For example, the materials operating in high-performance systems, such as jet engines , often reach extreme temperatures surpassing degrees Celsius, making creep a significant issue.

From steam turbines to nuclear power plants, creep limit is a key factor in design decision making , and rightfully so. In extraordinary circumstances, creep can lead to a building collapsing like the six story Royal Plaza Hotel in Thailand and in mechanical engineering it can be the mission critical factor in materials choice.

Generally, creep deformation occurs by grain boundary sliding , which means the adjacent grains or crystals within a material move as a unit relative to each other.

This means that the greater the grain boundary area, the easier it is for creep deformation to occur. Therefore, a larger grain size can improve creep strength, and this depends on the processing of a material. While creep resistance often results in the damage or microstructural degradation to a material, for some materials, like concrete, moderate creep is welcomed.