(~2,400 km away)

N. American PlateCocos Plate

Puebla

The Cocos (subducting) and North American (over-riding) tectonic plates converge in a northeast-southwest direction. The Sept. 19, 2017 earthquake occurred as a result of normal faulting at the top of the Cocos plate, and it bends and descends beneath North America (cross section, below).

“P” and “S” mark arrival times of primary and secondary waves across Kentucky. Up-and-down surface-wave displacements in mm are labeled at selected locations.

USGS Source Mechanism

This mechanism indicates normal faulting on a deep, southwest- or northeast-dipping fault plane.

W-Phase Moment Tensor (Mww)Moment 6.381e+19 N-mMagnitude 7.1 MwwDepth 50.5 kmPercent DC 100 %Half Duration 9.94 sCatalog USData Source USContributor US

Nodal PlanesPlane Strike Dip RakeNP1 108° 47° -98°NP2 299° 44° -82°

Principal AxesAxis Value Plunge AzimuthT 2.153e+21 N-m 28° 49°N -0.165e+21 N-m 6° 316°P -1.988e+21 N-m 61° 215°

Very strong shaking was experienced (see modeled intensity contours, above, and Felt Reports, far right) in some of the same regions shaken by the devistating Sept. 19, 1985 magnitude 8.0 Michoacan earthquake (32 years ago, to the day) and by the mag-nitude 8.1 earthquake, which occurred on Sept. 8, 2017 (inset map, above). All three earthquakes were related to ongoing convergence between the Cocos and North Ameri-can tectonic plates and both of the Sept. 2017 earthquakes occurred within the Cosos plate.

100˚W 95˚W

15˚N 15˚N

20˚N 20˚N

PUEBLA, MEXICOUSGS Community Internet Intensity Map

Sep 19 2017 01:14:39 PM local 18.5838N 98.3993W M7.1 Depth: 51 km ID:us2000ar20

Processed: Thu Sep 21 13:26:24 2017 vmdyfi1

Mexico

Guadalajara

Leon

San Luis Potosi

Acapulco

Aguascalientes

Queretaro

Morelia

Veracruz

Tuxtla Gutierrez

Xalapa

Villahermosa

Cuernavaca

Tampico

Pachuca

Victoria

Oaxaca

Uruapan

Tehuacan

Poza Rica

Chilpancingo

1789 responses in 31 ZIP codes and 257 cities (Max CDI = IX)

CITY SIZE

2M+

100,000+10,000+<10,000

100˚W 95˚W

15˚N 15˚N

20˚N 20˚N

100 miles

INTENSITY

DAMAGE

SHAKING

I II-III IV V VI VII VIII IX X+none none none Very light Light Moderate Moderate/Heavy Heavy Very Heavy

Not felt Weak Light Moderate Strong Very strong Severe Violent Extreme

USGS Felt Reports

Heavy shaking was experienced and deaths and significant damage have been reported.

Cross-section (A-A’ on map to the right)of subducting Cocos plate

Approx. plate surface

Approx. base of plate

Cocos plate surface,contoured by depth

trench

80 km

40 km

A

A’

Earthquake focusPotential fault orientationbathymetryseismicityreceiver function resultsseismic re�ection results

distance (km)

dept

h (k

m)

(http://earthquake.usgs.gov/earthquakes/eventpage/us2000ar20)

LLKY LOKY MOKY SMKY HEKY SOKY BHKY

ROKYEK20

EK32EK21

EK23

EK14

CUSSOFMKY

FLKY

EK22EK33

EK12

EK34

EK13EK26

EK35

EK36

HZKY

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_̂

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#*

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FMKY

ROKY

SOKY

FLKY

SMKY

HEKY

CUSSO

LOKY

BHKY

MOKY

LLKY

HZKY

Legend

#*

!(

#*

_̂

Weak Motion Station(velocity sensor)

Strong Motion Station(acceleration sensor)

Weak & Strong Motion Station(velocity & acceleration sensors)

Vertical Seismic Array(multiple down-hole sensors)

Temporary weak-motion station

KSSMN Seismic StationsStations with seismograms are labeled by name.

KSSMN Seismograms

1 mm(Fulton Co.)

1 mm(Univ. Ky.)

0.9 mm(W. Liberty)

0.9 mm(Louisa)

September 19, 2017 Puebla, Mexico (M 7.1)18:14:39 UTC / 12:14:39 at epicenter

University of Kentucky Kentucky Seismic and Strong Motion Network

1213 14

2622

21

2032

3334

35

23 36