PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

Global review of human-induced earthquakes

This chapter provides an overview of case histories that are exemplary of a broad spectrum of causative mechanisms and ranging from obvious to speculative in the correlation between earthquakes and specific human activities. Induced seismicity includes seismicity resulting from an activity that causes a stress change that is comparable in magnitude to the ambient shear stress acting on a fault to cause slip. On the other hand, triggered seismicity is used if the stress change is only a small fraction of the ambient level. The chapter considers examples chosen from many different regions to illustrate various mechanisms that relate human activities to stimulated seismicity. These case histories begin with mining-induced earthquakes for which the relationship between mining and earthquakes is unequivocal, and end with major earthquakes at midcrustal depths beneath oil and gas fields where a connection between the production and the seismicity is controversial. There are several measures of any particular activity that can be related to the total seismic deformation, which, in turn, can be used to estimate the maximum credible earthquake for that activity.

40 – Case Histories of Induced and Triggered Seismicity

Summary The arrest of a semi-infinite longitudinal shear crack is caused by either (1) the finiteness of available strain energy, or (2) an increase in fracture energy along the trajectory of the running crack. In the former case the following relationship may be used to evaluate the fracture energy: yo = RAa2/2ptn where yo is the fracture energy per unit length along the crack edge per unit extension of the cracktip (erg cm-2), R is the characteristic radius of the fault (cm), ACJ is the stress drop (dyne cm-2) and p is the rigidity (dyne cm-2). This leads to the following relationship: log Aa = -3 log R +f log (2ptny0) or from the Keylis-Borok relationship (1959): log Mo = 5/2 log R +* log (2ptny0)+0*64 where M, is the seismic moment in dyne cm-'. These two relationships are statistically acceptable for Southern California faults and the TongaKermadec Arc earthquakes. The fracture energy is found to vary from lo3 to lo9 erg cm-' with fresh fracture being associated with 10'-lQ9 erg cm-2 while frictional rupture with 103-107 erg cm-2. These values are in good agreement with other independent estimates.

The fracture energy of earthquakes

Induced seismicity related to geothermal projects versus natural tectonic earthquakes and other types of induced seismic events in Central Europe

Source study of the Lubin, Poland, tremor of 24 March 1977

The Belchatow, Poland, earthquakes of 1979 and 1980 induced by surface mining

A microearthquake survey in the Abu-Simbel area in Egypt

A numerical approach to the earthquake ground motion analysis is proposed for regions where no accelerograms are available. Using Haskell matrix techniques, the response spectra of a layered substratum for SV waves were calculated and then multiplied by the spectra corresponding to Brune's type pulses. The ground acceleration spectra were obtained for different angles of pulse incidence at the substratum base. The spectrum shape depends upon the substratum response and the pulse shape, while its level was related to the maximum ground acceleration corresponding to the expected maximum intensity. Transformation of the ground spectra into the time domain produced numerical accelerograms for horizontal and vertical components and for different angles of pulse incidence. Finally, a standard statistical procedure was applied to obtain the design response spectra used in engineering applications.

S.J. Gibowicz

Papers

Source study of the Lubin, Poland, tremor of 24 March 1977

The Belchatow, Poland, earthquakes of 1979 and 1980 induced by surface mining

A microearthquake survey in the Abu-Simbel area in Egypt

Numerical simulation of ground acceleration spectra and accelerograms for engineering application