Measures complex for earthquake effects prevention

To prevent natural dangers passive and active protective measures can be used. Active protection against natural hazards involves the construction of engineering structures, the mechanism of intervention effects, and reconstruction of natural objects, etc., passive – use (adaptation) of protective equipment. In most cases, passive and active protection methods are combined.

Main directions to ensure seismic safety of the people:

· Prediction of seismic hazard, proper warning of people and execution steps of safety instruction;

· Construction of earthquake-resistant buildings and installation in seismic areas. According to the rules these buildings and installations should be resistant to earthquakes of 7-9 points magnitude;

· Arrangement of settlements and enterprises should take into account the seismic character of this area;

· Knowledge of the precise rules of conduct and conditions of personal safety during an earthquake;

· Timely and efficient execution of works for the liquidation of consequences of earthquake.

Basic steps under conditions of earthquake effects:

· Permanently listen to the information concerning the situation and basic steps of safety instruction;

· notify neighbors and assist the children, disabled and elderly people;

· put on the floor hard things, fix things that can fall down;

· turn off gas, electricity and water systems;

· take necessary luggage and documents, reserve of food and medicines;

· leave the home or workplace and go to an open area or gathering place for residents evacuation as defined by state or local authorities.

Solution for the considered problem of seismic safety of population consists of a number of related tasks, the main among which is forecasting of earthquakes and emergencies associated with it, preventing earthquakes effects and responding to them.

Example: Assess the situation and an earthquake damage level of the manufactory at the distance (R) 50 km from the epicenter of the earthquake with a magnitude (I₀) 6 on the scale. The depth of the epicenter (H) is 30 km. The building is situated on fill-up soil. There is sandstone in the surrounding area of the manufactory. The building has foundation; material of construction is burned brick.

Solution:

1. Magnitude of the earthquake is recalculated from the formula (2.4):

.

2. Intensity I_R at the distance 50 km to the earthquake epicenter is determined by formula (2.5), scores:

Real intesity I_RE in the vicinity of the manufactory (2.6), scores:

With the aim to determine an earthquake damage level of the manufactory, it is necessary to define its type and aseismic stability according to Table 2.5: respectively the type of manufactory is Б2 and aseismic stability I_C =5.5 scores.

3. The difference between the real intensity of the earthquake and aseismic stability (Table 2.6):

Estimation data (Table 2.6) by the linear interpolation method allow to determine and conclude, that in the worst case the considered manufactory will experince the first (1) damage level with 30% probability.

4. The period of time, when the I phase of the earthquake (tremors) occurs, t_I, s (2.8) is calculated by following formula:

5. The period of time, when the II (main) phase of the earthquake occurs, t_II, s (2.9) is calculated by following formula:

Conclusion: Earthquake intensity, at the distance 50 km from the epicenter, is quite high with magnitude 5.5. Real intensity obtaines 6 scores. The manufactory can get weak damage (cracks in the plaster). The earthquake tremors will be felt in 10 sec. If you can not leave the house, turn off gas and electricity and stay near capital wall or at door aperture.

Example: An earthquake with a magnitude (I_o) 8 scores took place in the area of Vrancea (Romania). The depth of epicenter (H) is 200 km. Identify the earthquake effects for the residents in Yuzhnoukrainsk (number of people, N =300; material of building construction is burned brick) and in Odessa (number of people, N =300, material of building construction is concrete blocks).

Solution:

1. The magnitude is recalculated by the formula (2.4), scores:

2. The intensity I_R is determined by the formula (2.5), scores:

for Yuzhnoukrainsk, R =400 km:

for Odessa, R =200 km:

.

3. Real intesity I_RE of the earthquake in the vicinity of the residential building is assessed by the formula (2.6), scores:

· In Yuzhnoukrainsk the given residential building is situated on a granite slab. There is fill-up soil in the surrounding area of the house.

.

· In Odessa the given residential building is situated on fill-up soil. There is clay soil in the surrounding area of the house.

.

4. With the aim to determine an earthquake damage level of the manufactory, it is necessary to define its type and aseismic stability according to Table 2.5, respectively:

· the residential building in Yuzhnoukrainsk conforms to type B2 and aseismic stability obtains 6.5 scores;

· the residential building in Odessa conforms to type Б2 and aseismic stability obtains 5.5 scores

5. The difference between the real intensity of earthquake and aseismic stability is estimated in the following way:

· for Yuzhnoukrainsk: .

The house is stable to earthquake 5 magnitude.

· for Odessa: .

The estimation data (Table 2.6) by the linear interpolation method allow to determine and conclude, that in the worst case the residential building in Odessa will experince the damage of 3 degree with 40% probability.

6. The probability of population losses (Table 2.7) is assessed by the formulas (2.11, 2.12, 2.13):

Total losses (P_t):

Irreversible (lethal, P_ir) losses:

Sanitary losses (P_s): .

7. On the ground of relative population losses P_t, P_ir, P_s the value of absolute losses of residents in the bulding (construction is of concrete blocks) is recalculated by the formula (2.15):

Total losses (N_t), victims: .

Irreversible (lethal, N_ir) losses, victims:

.

Sanitary losses (N_s), victims:

8. The time period (t_I) of the 1 phase of the earthquake is calculated by the formula (2.8):

for Yuzhnoukrainsk: ;

for Odessa: .

9. The time period (t_II) of the II (main) phase of the earthquake is calculated by the formula (2.9), mins:

for Yuzhnoukrainsk:

for Odessa:

Conclusion: Real intensity of earthquake obtains 6 scores in Yuzhnoukrainsk at the distance 400 km to the epicenter. Real intensity of earthquake obtains 8 scores in Odessa at distance the 200 km to the epicenter. Based on calculation results it was cocluded that in the worst case the residential building in Odessa will experince the damage of 3 degrees with 40% probability. The earthquake tremors will be felt by people in 3 mins in Odessa and in 7 mins in Yuzhnoukrainsk. The main (II) phase of the earthquake will get Odessa in 4 mins and Yuzhnoukrainsk in 8 mins. The value of absolute losses of residents of the bulding (construction is concrete blocks) obtains 66 victims.

Key questions and tasks:

1. Can you give the definition of the natural disasters?

2. Which general mechanisms of natural disasters could you determine?

3. Which protective measure do you know to prevent natural disaters?

4. Give the definition of the earthquake.

5. Determine basic parameters and characteristic of the earthquake.

6. Determine the earthquake effects.

7. Determine the unit of measure of the earthquake.

8. Which protective measures do you know to prevent earthquake effects?

9. Give the definition of the landslide.

10. Which types of the landslide depending on the material do you know?

11. Which types of soil movement are involved into the landslide?

12. Can you define basic causes and triggers of the landslide?

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