Earthquake Ground Motion SimulationDuring 1992 Cairo Earthquake

At Saqqara Pyramid

Amin E. KhalilGeology Dept., Faculty of Science,

Helwan University

Motivation

The motivation of the present was initiated to help in the concurrent efforts to restore Zoser Pyramid after the severe damages encountered after Cairo Earthquake in October 1992.

Objective

Simulation of earthquake ground motion During the 1992 Cairo (Dahshour) at Saqqara pyramid to aiding the present archeological restoration projects there.

Presentation Overview

1- Area of Study.

2- Seismicity near Zoser Pyramid.

3- Site effects using H/V method.

4- Simulation technique (SMSIM).

5- Ground motion summary.

6- Discussion.

Area of Study

Damages in Zoser (Saqqara) Pyramid

Saqqara pyramid encountered severe damages. These damages is believed to be related to Cairo earthquake. Since 2003 efforts are exerted to restore the pyramid.

Earthquake activities near Zoser Pyramid

Cairo earthquake epicenter was only 14 km away from Zoser Pyramid. The magnitude of this event was about 5.8.

Previous study by Deif and Khalil (2002) pointed out that this event is the design earthquake for the area of Study

Site response using H/V method

• H/V method has received notable attention in recent years due to its low cost and relative simplicity.

• The method was invented in the 50’s of the last century, however, it was not widely used until the work of Nakamura 1989.

• Debates about the nature of seismic type involved in the estimation. Some believe it is Rayleigh wave type, others believed it is SH wave trains entrapped in the soil layers.

• The method gives the natural frequency with high accuracy, however, the amplification factor suffer from high uncertainties.

H/V field work

Ambient noise was recorded using k2-Altus Accelerograph. The time windows used was 5 minutes at a sample rate of 100 sample/sec. 25 recording points were selected mainly at the southern side of the Pyramid.

Sample H/V curves

Simulation Method (SMSIM)

This method was first based entirely on generation of stochastic (random) time series to imitate the overall shape of strong motion recordings. Afterwards the method is modified by using a representation of the seismic source to scale the simulated record. The input parameters are the magnitude, distance, and corner frequency of seismic source. Filtering and tapering of simulated time series to get a closer simulation of the overall features of the accelerogram. The SMSIM software (David Boore) to simulate the time series due to an earthquake of magnitude 6.3 (credible earthquake) at a distance of 14 km (at the site of Zoser pyramid).

Simulated ground acceleration

0.035

-1.50E+02

-1.00E+02

-5.00E+01

0.00E+00

5.00E+01

1.00E+02

1.50E+02 A

A

Response Spectra

per0.05

0.080.12

0.180.28 0.4

0.550.85 1.3 1.9 3 4.2 6 9 14

0.00E+00

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

3.00E+00

PSA response specra

PSA response specra

Discussion

The simulation of strong ground motion during Cairo Earthquake at Zoser pyramid showed that the peak ground acceleration equals 135 gal. The site response using the H/V method yielded a natural frequency of 1 Hz and amplification of about 1.5.

The result of the present work will help in the restoration projects at Zoser pyramid specially the proper solution to the shaft ceil of the pyramid.

Thank you