Chlorine 36 rock exposure dating

Armijo Northward view of the Magnola normal fault near the Forme village (Central Apennines, Italy). (b) Closeup view of the basal Holocene scarplet, showing the ∼10 m high vertical groove sampled by Palumbo Northward view of the Magnola normal fault near the Forme village (Central Apennines, Italy). (b) Closeup view of the basal Holocene scarplet, showing the ∼10 m high vertical groove sampled by Palumbo Cl concentration depth-curve for a limestone scarp section still buried under the colluvium has an exponential shape—just before an earthquake exhumes the scarp face (Fig. Once the earthquake has occurred, the newly exposed scarp section starts accumulating Cl concentration profile along the entire exposed scarp should take a shape made of a series of exponential sections separated by sharp discontinuities (Figs 2c and d).

(a) White arrows outline the Holocene fault scarplet, at the base of the cumulative escarpment (black double-arrow) which forms the relief. (a) White arrows outline the Holocene fault scarplet, at the base of the cumulative escarpment (black double-arrow) which forms the relief. Those discontinuities reflect boundaries between each major earthquake rupture, while the vertical separation between two successive discontinuities provides a measure of the displacements produced by the earthquakes. Recurrence time is 2 kyr, vertical on-fault slip 2 m, and pre-exposure duration 2 kyr. Left-hand panel shows fault and colluvial wedge geometry, together with earthquake exhumation history. Right-hand panel shows the evolution of the [ 2004).

However, interpretation of offset strata and fault-rupture related features is sometimes debatable, while the earthquakes cannot be dated directly (only soil markers can be used to bracket the event times) leaving large uncertainties (e.g. The second approach is based upon the cosmic-ray exposure dating of preserved, seismically exhumed normal fault scarps or 2004).

Reprocessing of the data helps to refine the seismic history of the fault and quantify the uncertainties in the number of earthquakes, their ages and displacements.

Recurrence time is 2 kyr, vertical on-fault slip 2 m, and pre-exposure duration 2 kyr. Left-hand panel shows fault and colluvial wedge geometry, together with earthquake exhumation history. Right-hand panel shows the evolution of the [Cl dating approach seems able to infer earthquake information, it is unclear how much uncertainty surrounds this information.

In this contribution, we assess the resolution of this method by examining the effects of all scaling factors that modulate the Cl concentrations (colluvium dip, density and chemical composition; scarp dip; upper eroded scarp dip; variable content of the samples in target elements; possible denudation of the scarp; geomagnetic field temporal variations; possible snow cover).

We find that the Magnola fault has ruptured during at least five large earthquakes or earthquake clusters in the last 7 ka, and may presently be in a phase of intense activity.≥ 6) are generally longer than instrumental and historical earthquake catalogues, and palaeoseismic methods must be used to infer the timing and magnitude of earthquakes in the geologic record.

However, there are only a few techniques that allow such past earthquake recovery.

199

Leave a Reply