GB/T 17742-2020The Chinese seismic intensity scale (English PDF)

2.1 Terms and definitions

The following terms and definitions apply to this document.

2.1.1 Seismic intensity

The magnitude of ground motion caused by an earthquake and its impact.

2.1.2 Damage index

A quantitative indicator of the degree of seismic damage to buildings.

Note: A number between 0.00 and 1.00 indicates the degree of damage from light to severe.

2.1.3 Mean damage index

The weighted average of the damage index of similar buildings.

Note: The mean damage index is the sum of the product of the proportion of buildings damaged by the earthquake at all levels and the corresponding […]

3.3 Types of buildings for assessing intensity

The buildings used to assess the intensity include the following five types:

a) Category A1: Civil, brick, stone and wood buildings without seismic fortification;

b) Category A2: Bucket timber frame building;

c) Category B: Brick-concrete structure without seismic fortification;

d) Category C: Brick-concrete structure buildings with seismic fortification in accordance with degree VII (degree 7);

e) Category D: Reinforced concrete frame structure building with seismic fortification in accordance with degree VII (degree 7).

3.4 Building damage level and its corresponding damage index

The building damage level is divided into 5 levels: basic intact, slight damage, moderate damage, severe damage, destruction. The definition and corresponding damage index d are as follows:

a) Basic intact: The load-bearing and non-load-bearing components are intact, or individual non-load-bearing components are slightly damaged, which can be used without repair. The corresponding damage index range is 0.00 <= d < 0.10, which can be 0.00.

b) Slight damage: There are visible cracks in individual load-bearing components; there are obvious cracks in non-load-bearing components.

It can be used without repair or with minor repairs. The corresponding damage index range is 0.10 <= d < 0.30, which can be 0.20.

c) Moderate damage: Most load-bearing components have slight cracks; a few have obvious cracks; some non-load-bearing components are seriously damaged and can be used after general repairs. The corresponding damage index range is 0.30 <= d < 0.55, which can be 0.40.

d) Severe damage: Most load-bearing components are seriously damaged; non-load-bearing components partially collapsed; building repair is difficult.

The corresponding damage index range is 0.55 <= d < 0.85, which can be 0.70.

e) Destruction: Most of the load-bearing components are severely damaged; the building structure is on the verge of collapse or has been destroyed; there is no possibility of repair. The corresponding damage index range is 0.85 <= d <= 1.00, which can be 1.00.

4.1 Evaluation method

4.1.1 The multi-index method of macro-survey and instrument determination can be comprehensively used in the evaluation of seismic intensity:

a) For areas that do not have the conditions for measuring seismic intensity by instruments, macroscopic surveys shall be used to assess seismic intensity.

b) For areas with the conditions for measuring seismic intensity by instruments, the seismic intensity measured by instruments should be used.

4.1.2 Evaluate the seismic intensity according to the seismic intensity levels as classified in Table 1.

4.2 Macro-survey for evaluation of seismic intensity

4.2.1 The process of macro-survey for evaluation of seismic intensity includes survey area and route planning, seismic damage investigation and analysis, comprehensive determination of seismic intensity, drawing of seismic intensity map.

4.2.2 The content of the macro-survey includes the seismic damage of buildings, human feelings, reaction of objects, lifeline engineering seismic damage and other seismic damage phenomena. The average damage index shall be calculated for building seismic damage.

4.2.3 According to the survey results, comprehensively considering multiple evaluation indicators, evaluate the seismic intensity according to Table 1.

4.2.4 When evaluating the seismic intensity through a macro-survey:

a) Degree I (degree 1) ~ degree V (degree 5) shall be based on human perception and the reaction of utensils as the main evaluation basis;

b) Degree VI (degree 6) ~ degree X (degree 10) shall be based on the main […]

A.3 Baseline correction

Baseline correction processing shall be performed on the ground motion records; the recording time process should be used to subtract the arithmetic mean value recorded before the earthquake event. The length of the pre-event recording time should be 10 s.

A.4 Record conversion

When the ground motion record is acceleration, it shall be converted to obtain the speed record. When the ground motion record is speed, it shall be converted to obtain the acceleration record.

A.5 Digital filtering

Each component of the ground motion acceleration and velocity records shall be filtered by a digital filter of 0.1 Hz ~ 10 Hz. It should use the minimum phase filter. The filter passband ripple shall be less than 0.5 dB; the filter out-of-band attenuation shall be greater than 12 dB/oct.

A.6 Record synthesis

Use the formula (A.1) to calculate the three-component synthesis acceleration record:

Where:

alpha (ti) - The synthesized acceleration value at the time ti, in meter per second (m/s2); […]